My only questions is how did he go into "it is not your fault, and it is not my fault. It has nothing to do with you, and it is something that cannot be changed" without breaking up with you then? I mean, did he specify the it, or did he just say he wasnted to talk about it later.
I don't know about breaking up with him first, because you don't KNOW that's what's wrong. Maybe he just has a problem that the relationship can survive. But, you should go and ask him if he has anything he needs to say or talk about, if you're tired of being in suspense. Or tell him he's been acting differently, and ask why.