A similar thing happenned with me actually. My teachers thought I had dyspraxia when I was 14, but it wasn't flagged up as anything else until I was in my last year of sixth form.
Uni has been extremely difficult! Especially because I changed uni halfway through the term and now don't know anyone, which makes it worse. I'm useless socially anyway, so that didn't help really.
So what are you up to now that you've quit uni? I've been slightly tempted all year to drop out, but I'm going to try another year and hope for the best (fingers crossed!) Hopefully being there the full year will make a difference but I don't know.