sounds like he wants to break up but wants you to before he does. There is one instance where I have done what he is doing and it was the first couple months after my boyfriend went to university 4 hours away and I was scared I was holding him back
Ask him why he keeps asking you. It's only 1 of 2 reasons in my opinion. He's either really insecure and self conscious (depression etc), doesn't believe you really like/love him or 2) he wants to break up but doesn't want to be the one to do it.