Hi,
I just wanted to remind you that your A-level results aren't everything. I left sixthform in 2016 with only 2 A-levels ( Grades C and D) and i'm studying Biomedical science at uni right now. I experienced the same as you at school so my advice for you is just to focus on your revision, work as hard as you can, improve your revision technique and really try to prove those people wrong.
If you don't do well, its not the end of the world and possibilities are out there for people who don't excel in their A-levels (foundations years and UCAS clearing for example)
Most importantly, your health should always come before any academic achievement and your grades do not define who you are or your success as a person. Don't let the pressure of your friends and teachers put you off.
Good luck!
xx