It's got to the point where I don't know how to go back to my old happy self. I don't know whether I should seek help or not. I just feel stuck.
Definitely seek help! First port of call should be your GP and when you see them be as honest about how you're struggling as possible so as to receive the correct help/treatment. Without help not much will pull you out of it unless you're suddenly really happy with your life and you have great social support all over a sudden which if that was the case you likely wouldn't be suffering the way you are so... make an appointment with your GP and have that chat
Basically what the other poster said, see your GP, be honest and get help. This first step can really help you on your way to deal with your depression. Keeping it all to yourself for a long time isn't good or beneficial to you.
It's got to the point where I don't know how to go back to my old happy self. I don't know whether I should seek help or not. I just feel stuck.
I know every one is very quick to suggest going to see a GP, but it really does need to be considered alongside other things such as your lifestyle, your daily activities, support networks etc.
It really depends on the individual. What helps one would be useless for another, and it's very much a gradual learning process. Unfortunately a mental health condition isn't something you can necessarily fix, it's something that has to be learnt to manage.
Immersing yourself in physical activity may help. There is a strong link and it's something that keeps me going. Reaching out to someone you may trust, ringing samaritans to help you get through some troubling thoughts etc. Maybe it doesn't help you to talk- maybe it's best to be alone. Give-volunteer, do something rewarding in your spare time, depending on your interests.
It's very important to look at the wider picture and almost evaluate your life. It sounds heavy but it doesn't need to be done instantly- again, it's all a gradual process.
As others have said, seek help from GP and local community services.
It's also very important that you try to not lose control of your daily routine so much, this diagram best illustrates what I mean:
Essentially if you keep reducing the behaviour you do (e.g. don't go to school/work or don't do your hobbies or don't do housework) then you feel worse and worse.
It's difficult but you can definitely bring yourself out of depression and professional hope would be a great start