I dont understand if he wants me or not?Confused.

I've been with my bf for 8.5 years, we where young wen we met i was 15. We both love eachother but i have found over the years we have alot of problems over unecessary things, he has a short temper and yells at me over the most smallest things, he likes to joke around in a rude way commenting on things about me, he always breaks up with me and after a few days later he is fine, but i think the problem is he is scared to commit, because when we start becoming good in the relationship..he goes and screws it up, last year we broke up for 4 month which was the most we ever have, everything was going down hill and i couldnt handle it, but in the end we realised we both needed eachother and now he is doing the same as he did before.
Im tired from all this, i really want to be happy and im struggling again to do so, can someone please give me any insite of what i should do,a litle advice is great.Thanks