Mock results and future

Sorry that your teachers laugh at you, that’s not professional of them at all and they should be helping you.
It’s possible to bring your grades up with a lot of hard work and time put into it. You need to identify where you’re going wrong- is it content? Or do you know the content but can’t get the exam technique down? A combination of the 2? Nerves getting to you in the moment? Whatever the issue is you need to focus on it.
If it’s exam technique, you need to do past paper questions and practice practice practice. This was my issue with biology a level where I got an E on my first mock and got a B on the actual thing. Past paper questions and learning the mark scheme saved me lol
If it’s the content maybe you need to review your revision techniques and try something else. You could do mind maps/dumps, flashcards, quizlet etc but highlighting/reading will not cut it.
If it’s nerves, you need to try to find techniques to calm you down ie breathing, 5 senses technique etc. If you need counselling you can get that through your school.
Would tutoring be an option for you? If it is, maybe look into that. If it’s too expensive, then do some past paper questions and get your teachers to mark them for you. If they laugh, report them for not doing their job. You’re only going to be as good as your teacher allows you to be, so it reflects badly on them.
I hope it all works out for you and you can find what works for you Unfortunately, A-Levels are a massive jump up from GCSEs and you will have to put a lot more work in where you might not have to had before.

I've been told that for geo and my one history class that I'm not structuring my answers the right way. Content isn't too much of an issue
However, my other history class I have zero faith with. The content is really hard for me to remember and well as structuring too. My AS history is separated into two classes with two different topics (Nazi Germany & The Stuarts). My Nazi Germany class is mainly a structuring issue and my teacher has offered some support. It's Stuarts that's the worst. My teacher there says that I need to get a grip, pull my finger out and do the work.
Fortunately for me I've never had bad nerves, maybe some slight worry but nothing overpowering

Have they told you what you're doing wrong structure-wise? As in, have they said 'you're doing x wrong so you need to do y instead'? If not, try going back and asking them. I know it probably seems horrible to have to talk to someone who won't take you seriously, but it's their job to provide help where you need it.
In the mean time, you could ask for/look up sample answers (perhaps in the examiner's reports of past papers etc) and try copying the styles that do well. Pick out what you're doing differently and try to adopt the better techniques. Well done for getting the content down for 2 subjects, that half of the battle!
As for the other history one, what methods have you tried to use for remembering the content? Sometimes a technique will work for one subject but not another and it's up to you to work out what works for you. Remember, to get a decent grade you don't need to remember every single thing. Try to identify what the most important parts of each subtopic is and start there. If you get the basics down, you'll find it so much easier. No one can remember every single fact about it, so maybe limit the amount of facts you try to remember at first, and then you can work your way up once you know the essential things off by heart. (Does that make sense?)
Much the same with exam technique as the other subjects- study exemplar answers and try to convey that in your own structuring. Learn what specific style they want- do they use a specific acronym for paragraphs such as PEE etc, do they want a specific essay structure such as Intro, 3 points, try to link them together, conclusion etc
As much as you might not want to do it, you'll probably have to do lots of liaising with your teachers to get to grips with it all. Don't let them belittle you, and show them how much you care about doing better. They probably think you just don't care about doing well, but clearly you do, I'm just sorry that that's not conveying for you in your grades yet

That's a really sucky situation 😕 I mean with AS Levels you just need to pass to move onto the next year, they won't even matter once you have further qualifications. If it's going to make your mental health worse to spend a lot of time on it, try and get to a point where you can just pass. It's not worth wrecking yourself over. Socialising and being a teenager is just as important as school, so make sure you're having fun and taking breaks as well. As I say, it's going to be hard but it shouldn't be impossible. Do they have anything in place for you if you have extra needs? You've so got this though!

Unfortunately I'm not able to receive any kind of help in exams whether it be extra time or a separate room even when I've expressed to the college about how I feel the need it'd really help, but it is what it is right 🙃.
I mean, I know that I just need to pass. If I'm right in saying that even an E is a pass and I can get to the next year I'd still be glad. But I've been told don't bother if I don't get a D at the minimum.
Thank you though! Gonna make sure to try hard to get enough to just pass, I know I'm doing the best I can. Even if my best won't be a D, I tried regardless