Low mood - should I/how to tell parents?

Sorry if this is a bit all over the place and for the long post but it feels difficult to put all my thoughts down in a coherent way.
So for a while now I would say I've been feeling kinda low and overall just a bit meh, there are times that I feel fine or happy but I think it seems to be more of the former and I find that if I am happy/fine for example it doesn't take much for my mood to switch. I can't exactly pinpoint a specific cause, I think it's probably a build up of different things/emotion and me just trying to get on with it.
I know that I suffer from low self esteem and confidence which I would say was pretty much caused by bullying in school so I think that's been in the background ever since which obviously won't help with my mood.
Anyways I recently had a day out with family and I felt fine for the most part until we went to do some activities and I don't really know what it was that triggered me (I think caught a glimpse of myself and I was feeling bad about myself/appearance and probably didn't want my family to make comments if I wasn't good) but I didn't want to take part and I just felt annoyed and upset ending up crying in public and refused to take part.
Seeing other people living life, feel happy and just enjoy moments makes me feel upset because I want to feel like that too but I feel like I can't, I'm always overthinking or feel self conscious. I also felt guilty because my parents did this to make me feel happy and there I was upset ruining the day out.
So after this my parents asked me what's going on. I have wanted to tell them at times and thought I would tell them about my low self esteem at least this summer so maybe I could get some CBT for example because I don't want my whole life to pass not being able to properly enjoy things. However, sometimes I think that I'm fine and maybe I don't need to make a big deal of it and somehow I'll just get over it. It feels quite difficult to open up to them about emotional issues as we have more of a stiff upper lip mentality. I'm worried about how they'll react and that they'll just see me as being weak or just crazy. When I was bullied I felt that I was a burden for them because I was struggling emotionally and although they tried to make me feel better by taking me out ect it felt like they didn't know how to emotionally support me.
In addition, family may find it hard to understand why I feel this way because from the outside I'm still able to function, I'm doing well with my education and have achieved various things. When they say things like to just enjoy life, being young because it's the best time of your life and to just be confident, it makes me feel frustrated because it's not that easy, if I could I would.
I'd just appreciate any advice really or tips on how to improve my situation and if/how I should go about telling my parents. It's so difficult because a part of me wants to tell them but something is stopping me from doing so.

Hi! I want to start this by assuring you that you are really not alone right now. Everything you said in this post resonated with me greatly; as someone who has been bullied, has emotionally challenging parents and persistent (yet sometimes fluctuating) low mood.
Firstly, you are absolutely worthy of getting help. Something a lot of people don't realise about depression - especially high functioning depression (which this sounds awfully similar to, with the good academic performance and extracurriculars) - is that you don't need to be low all of the time to be depressed. Those moments where you're okay are extremely confusing, I know, because it's almost like you try to convince yourself the low times aren't THAT bad if you can still be okay. This isn't true. Your emotions and feelings and experiences deserve to be taken seriously.
If you want to tell your parents but are unsure how, then I am firm believer of writing things down. From this post alone, it seems like you're really good at this. Whether this is in a text or a letter, this could be an option. It doesn't have to be detailed. Even something simple, such as when you're in school/college/uni (idk how old you are) so you don't have to immediately deal with a potentially uncomfortable conversation.
I do believe that therapy is a good idea. If that's inaccessible, then speaking to a teacher, friend or your parents is definitely something you should do. I personally accessed counselling services outside of my college. They were able to refer me, my parents had no idea, and I was able to receive six weekly sessions this way. I think exploring your options through your school is a good option for this reason. If you're worried about accessing school counselling, then I would speak to a teacher about confidentiality first.
Most schools have a duty of care to report anything that means you're in harms way. If you express thoughts or experiences of this nature, they'd probably have to tell your parents. But, if you are safe, then speaking to somebody in school shouldn't be an issue in this regard.
The conversation of getting help is always the most difficult. But, trust me, you want to do it now. I let everything escalate and things became far worse. You DESERVE help. You have been through so much (I'm pretty sure bullying can be a form of trauma). And now this low mood is interfering with your daily life. I don't know your situation with friends, but if that's an option, reaching out to them would also be a good idea. You'd be surprised how many people struggle with everything you have described. Just having someone to empathise with you can sometimes mean the world.
If all of this sounds too daunting, I can reply to this with a non-anonymous post so you can message me about whatever is on your mind. You're not alone!!!

No problem at all! I'm glad it was helpful 🙂
I got counselling after writing a note to the wellbeing team. I didn't even read it out, I just handed it over and they helped me with a referral. This was only because they had a partnership with a private team, so I don't know how common this is.
If you feel uneasy about reaching out to the wellbeing team (which I would recommend - it's scary but definitely worth it!) then I know that self-referrals on the NHS are possible. Of course, this is made harder by the likely painfully long waiting list, so going through your university or even the GP would be better I can imagine.
It's definitely worth googling it though. I'm in Wales, so I can't access it, but I've seen something to do with free services on an NGO in England? https://hubofhope.co.uk/ - it might be worth visiting this and seeing what's available to you!
But definitely remember that you DO deserve help and you're absolutely not alone! I'm rooting for you 🙂

Sorry if this is a bit all over the place and for the long post but it feels difficult to put all my thoughts down in a coherent way.
So for a while now I would say I've been feeling kinda low and overall just a bit meh, there are times that I feel fine or happy but I think it seems to be more of the former and I find that if I am happy/fine for example it doesn't take much for my mood to switch. I can't exactly pinpoint a specific cause, I think it's probably a build up of different things/emotion and me just trying to get on with it.
I know that I suffer from low self esteem and confidence which I would say was pretty much caused by bullying in school so I think that's been in the background ever since which obviously won't help with my mood.
Anyways I recently had a day out with family and I felt fine for the most part until we went to do some activities and I don't really know what it was that triggered me (I think caught a glimpse of myself and I was feeling bad about myself/appearance and probably didn't want my family to make comments if I wasn't good) but I didn't want to take part and I just felt annoyed and upset ending up crying in public and refused to take part.
Seeing other people living life, feel happy and just enjoy moments makes me feel upset because I want to feel like that too but I feel like I can't, I'm always overthinking or feel self conscious. I also felt guilty because my parents did this to make me feel happy and there I was upset ruining the day out.
So after this my parents asked me what's going on. I have wanted to tell them at times and thought I would tell them about my low self esteem at least this summer so maybe I could get some CBT for example because I don't want my whole life to pass not being able to properly enjoy things. However, sometimes I think that I'm fine and maybe I don't need to make a big deal of it and somehow I'll just get over it. It feels quite difficult to open up to them about emotional issues as we have more of a stiff upper lip mentality. I'm worried about how they'll react and that they'll just see me as being weak or just crazy. When I was bullied I felt that I was a burden for them because I was struggling emotionally and although they tried to make me feel better by taking me out ect it felt like they didn't know how to emotionally support me.
In addition, family may find it hard to understand why I feel this way because from the outside I'm still able to function, I'm doing well with my education and have achieved various things. When they say things like to just enjoy life, being young because it's the best time of your life and to just be confident, it makes me feel frustrated because it's not that easy, if I could I would.
I'd just appreciate any advice really or tips on how to improve my situation and if/how I should go about telling my parents. It's so difficult because a part of me wants to tell them but something is stopping me from doing so.

Hi, sorry to hear this I did CBT through the NHS my parents were supportive cos this was a long time after I had opened up waiting lists are long but when you get your assessment if it is really bad (aka you're at risk) you get bumped up as its marked as urgent, CBT was probs the most helpful thing ive done and ive done a lot of therapy. When my issues started I didn't know how to tell my parents I went to someone at school had a meeting and they explained it to my parents which was daunting but was the best thing for me as I was way too scared to do it alone I would recommend going through school, directly calling cahms urself for an assessment (make sure u mention u have looked into cbt thats what I did) or if you have someone in ur family u trust having them present to help you explain (its common to freeze up or not explain properly when ur on ur own) writing down what u want to tell them could also be a good idea so you can properly explain. hope things get better for u at the end of the day ur mental health is the priority the longer u leave it the worse it'll get its scary to tell people but its for the best if ur parents aren't supportive this doesn't mean you cant still go down the route of getting yourself help.