Maybe not AAB, but it's certainly possible to improve your grades to CCC or sth...
Don't try to study everything. Instead focus on exam technique. Prioritise the types of questions that have higher marks. Download the marking schemes and answer according to what's on there. Unless you're explicitly told otherwise, of course.
Not sure what board you're on, or how things have changed in the last 5-6 years. However, when I took my A-Levels 5-6 years ago, that's what I did and it improved my grades drastically. I'm pretty sure i'd have managed to do even better had I done Edexcel (modular) instead of CIE, which was linear, meaning that I had 14+ papers in the same exam period. Oh and the multiple choice questions were often very similar.
That's what I did to improve my A-Level grades. Same with GCSE biology as well. I only took the actual exam once and got a B, but frankly, it was purely exam technique. I didn't know most of the stuff being covered. I just practiced the multiple choice paper like a maniac and lo and behold, the questions were very similar. Same thing with our alternative to practical paper. I answered what I could for the theory/essay based questions and the rest I just BS'd.
Depression and anxiety are tough to deal with. Try not to set impossible goals for yourself. That will only serve to overwhelm you and cripple you into inaction. Do what you can, whatever little it is. Every little thing you do is better than nothing.
In the end, if it doesn't work out as well as you thought, it's not so bad. You'll take your time to get better. You still managed to pass your A-Levels, which is great.This means you can actually go to uni. Some top unis may let you into a foundation course. Or you could start directly somewhere your future/current grades give you access to. If you do well there, it won't matter. You can build upon that and apply for a master's at another uni of your choice.
All of this to say, don't sweat it too much. Do your best. No point fretting over details. Take that energy and invest it in studying. That's the best you can do right now.
Oh and another thing is, you might want to consider taking another A-Level for one of the subjects you got an E in. Some of the essay based subjects shouldn't be too hard to study. Maybe you're just tired of doing the same thing? I dropped chemistry 4-5 months before my exams for an A-Level in a language I was good at and did alright. In retrospect, I probably should've dropped physics for history or sociology.