Hey, thank you all for your answers.

Last night, he was looking at some of his test results with a sad expression on his face, so I asked what was wrong. He responded, angrily, that he should have left me back when he had the chance. Now it's too late, because his doctor is testing him for some autoimmune disorder, which apparently is brought on by stress, so by me, since I am the main source of stress in his life.

I was hurt. After some angry back-and-forth, I told him if that what's he feels, he is free to go on his merry way, and left the room. I was crying, so he came to comfort me. We managed to talk calmly after a while, and he basically told me that he has been miserable in our relationship, he feels better when he is alone, and he only entered a relationship with me, and then moved in, because he though that he would paint and travel a lot and he wouldn't have to spend too much time with me. (You'd think something like this would have come up in these four years, but better late than never, right?)

This obviously broke my heart, because to me the point of a relationship is wanting to share your life with someone; if I wanted a FWB then I would spare myself the hassle of it. I'm also a little miffed about it, because I am usually very explicit about my wants, needs and expectations, and I don't think I ever pushed him for anything - I have never once given an ultimatum. Anyway, at least it makes sense, and it's something that really has to do with our relationship. He also listed his abhorrent behavior as one of the reasons we shouldn't be together anymore, because he hates himself for it. He didn't apologize for it, but he didn't openly blame it on me either. In general, he said that my presence doesn't help him be the person he wants, and he wants to break up.

And then he asked me to sleep with him, because I guess the power of boners conquers all.

And that, folks, was the story of how we broke up. I'm on the "no-one will ever love me because I'm not worthy of anything" train at the moment, and haven't stopped crying since, but I'll be fine.