Frankbtl has some good advice.

Your boyfriend is trying to manipulate you by making you feel guilty about how he chooses to live his life. It's really unfair to you.

Practice your response to him saying that he will revert to his old ways. Something like "I'll be really sad if you go down that path, but if that is how you choose to live your life, I can't stop you" -- or whatever works for you and your situation. I think the important thing is to get a line in your head that you can call up almost on reflex.

I would also think about how you want the move to go (assuming you want him to move out?). Decide what your boundaries are now. How much time will you give him to find a new place? What will you do if he ignores your deadline?

Good luck -- it sounds like an awkward situation!