Never feeling good enough

I chose Chemistry, Biology and Maths A-levels and I want to do computer science

(not the ideal subject combination I know - but I guess this is what happens in the floored education system where immature 15-year-old me had to chose my career path).

Even though I achieved 3A* looking through the student room fills me with so much anxiety as some people applying to the same unis as me have 5A* predicted and have Fmaths, maths, compsci, physics and whatnot.

All the universities I applied to only require A-level maths but I feel so inadequate.. This is what I want to persue but its just hard to see so many others have the things you lack. Like why would universities even accept me

The most important thing you can do for yourself is focus on yourself and what you want to do. Looking at what others are doing is distracting and can be really bad for your mental health. Follow your path and don't let anyone deter you from that path. Also, don't put pressure on yourself, relax and don't let the education system and grades influence whether you're happy or not.