I just have one question...

My ex boyfriend broke up with me and tells me he doesn't think he can be in a relationship with me anymore. He tells me he cares about me. But right before we broke up he was talking marriage and buying a house, building a future, etc. We have lived together for two years now.

His decision just seems so rash. Do people really do that? My instincts tell me that he got scared of our relationship. We have been arguing and fighting a lot because of extra stress from school. He says that that's not what he envisions for himself. I know he still loves me a lot but he says he just wants to be alone and do his own thing. I'm just so confused because I felt that things were getting better. Our fights weren't as big. But then he just broke it off. And like I said, he was talking marriage literally a week before we broke up.

Just because the fights weren't as big doesn't mean they didn't take a heavy toll mentally. He could have gotten tired of all the little fights and just decided it's not worth it anymore.

Obviously he wasn't as serious, or committed as you think. I think he was just feeding you what you wanted to hear, to get what he could out of this. So sorry, as I have read your other posts, and know you have a large hole in your soul, and are still in a bit of shock, as your world is topsy turvy right now.
Try to be patient with yourself.

He could've gotten cold feet, he could've found someone new, or something else might've happened but what matters now is that he's gone and you have to concentrate on you. Only he knows the reason why he broke it off with you but the at the end of the day he's gone and you need to concentrate on you and NC.