A levels really aren't a true indicator of anything, they just show your willing to work hard enough at university. I only got BBC in Physics, Maths and Biology, came top 10% in my class at undergrad and now I'm studying theoretical physics at Imperial College.
You'll figure out whether your naturally able in any particular subject when you go to university, like I say anyone with a brain cell and enough motivation can get good grades in GCSE and A level, personally I did not have the motivation...