Hi!I totally get how you feel. I currently suffer with severe depression and anxiety and your feelings and situation are very similar to my own (I'd even say almost identical). I am also in my final year of A-levels and like you I wanted to go to uni but I was, and to an extent still am, very mentally and physically drained.
Honestly, the best advice I can offer you is to take away all of that stress. I've decided to take a gap year to take the stress off a-levels and getting into uni, because by next year I'll know whether I can/or can't get in, which takes away that extra pressure. Also, I know that it isn't ideal, but have you considered postponing your exams until next year, or just taking some of them this year?
Your parents are here to support you, and help you. If they are getting worn out by you, which is something you probably perceive (trust me I've been there), then maybe try explaining your thoughts to them personally or via someone else like a teacher or school nurse perhaps? I find that writing things down helps. I feel that my teachers are frustrated with me, so I occasionally write down my thoughts/feelings on a piece of paper and just give it to them without really saying anything else, (I use The Mighty's posts to help me formulate this stuff).
I also fully understand the whole meds thing, but in the end they can only take you so far, the rest is up to you, which sounds like useless advice but I've just figured that out for myself, though I still am on the meds...Talk to your GP about the eating/sleeping. Mine put me on sleeping pills a few days ago and they've temporarily made life a lot easier. Also, with concentration and motivation, if 30 mins is all you can do, then just stick with it and don't worry about it (my limit's about 20 mins), and slowly try building yourself up to 40 mins etc.
Most importantly, listen to your body. Don't try to fight it because I can tell you that it only makes things worse. If you can't keep your eyes open, maybe thats your body's way of telling you that you need to rest so dont try to keep them open. I nap for about 3 hours after school and Ive tried fighting it but it just made things worse.
Hope that helps and remember you are not alone. 🙂
If you need anyone to talk to I'm here. 😊