I want to break up with my boyfriend, except I already told him I'd support him when he goes back to uni.
That sounds complicated. Wouldnt you feel bad for breaking up with him after you said you'd support him at uni?
I know that's it's wrong but I don't care anymore.
If you have made promises to your boyfriend, then you should keep them if you are able. If you aren't then you should be honest with your boyfriend and break things off with him and not drag it out.
I'm going to ignore this advice.
Well you're going to have to choose one or the other before it blows up in your face. You can still support him and be his friend at Uni even if you decide to break up. Next time think about what you actually want instead of making promises you can't keep.