have you thought about going to a less competative uni? if your doing a course you enjoy, then aslong as you like the uni it will be fine, and if you dont think the competativeness will be good for you then is it worth risking your health over to push yourself so much to go?
i went to a crap uni, infact when i went it was a university college, because i didnt get the grades, but im so glad i chose that uni because i fit in with most people on my course, yeah there was academic people with really good GCSEs but then there was lots like me that wernt so clever. and i think id have done worse at a better uni honestly...
also, there are 9 ways to be clever, so dont say your not because you ARE
but you dont need to think about it right now this second, but it is worth thinking about your options hun, even if you dont go to uni this year, look at next year when youv had a year out