If you're going to break up, you should do it now. It must be hell staying with someone when you know you won't be together in a few months time. Basically, now you're just f*** buddies, since obviously you're not happy.
Accept it, split for a while, it will be difficult but obviously he has doubts and I'm sure you don't need to stay with someone who feels your relationship has no future.
If you do miss each other while at uni, then surely you can try again. Then you'll both know what uni is like, you'll be together because you want to and there wont be any doubts in your heads as to what you could be missing out on.