How to cope with a boyfriend with borderline personality disorder?

How do I cope with this he can never make up his mind about anything and it’s so confusing. One day he is quitting smoking and is going to throw away any cigarettes he finds on me and the next day he is asking if I have a cigarette and a light. One day he wants to stop having sex because he’s terrified I’ll get pregnant (why he’s so worried I don’t know) and to prove to me that’s not all he wants and the next day I’m having to rip his hands off my zipper. I barely know who he’s going to be on any given day. help! :(