Um, If I am to put my two cents in here, perhaps I might suggest ADD/ADHD? I am in the process of consulting my doctor about this through referral, and it seems very likely this could be the case..
Do not by any means take this as a negative thing or a judgement.. It may be something to look into.
I have struggled with examination and general life for a long time... Losing things, forgetfulness, missed appointments, inability to focus in class etc and since my referral and after some research everything seems to be coming together with this realisation..
There are peopel who can help and Access and Foundation courses you can do. Just consult your doctor and explore your options and your symptoms.
(Just to clarify, I do not believe ADD/ADHD to necessarily be a disorder, but very possibly a different type of learning style. Alot of ADHD diagnosed adults are functional and highly creative/intelligent people, it is all about coping skills. If this turns out not to be the case for you, there are ways to cope and there are people who will be willing to help you. DO NOT give up.)
Alternatively, consider what you actually want to do or be in life. University seems like a great option but there are many amazing experiences to be had in life that do not require formal education. Especially things like starting a business or volunteer/charity work!
Best of Luck and keep your spirits up!