Everything should have been worked out in advance, complete with penalties for late delivery. If he is unwilling to provide a schedule, and it is not in the contract in some form, you may have to find another builder. You would owe your current one for work completed.

You should have a contract that ties payment schedule to certain benchmarks of completion. That might be a motivator. Your situation is not uncommon from my experience. I think contractors are for the most part terrible business people. They make simple procedures completely nerve wracking. My guess is he does not want to commit. If he gets another job in that he can squeeze into your schedule he probably wants to leave the door open to do that.

In an ideal world I agree with what sooz001 says, but in reality, where I live, I have never talked to a single contractor who does business like that. Finding another builder would simply mean starting the headache all over again with someone who is bound to give you the same kind of service.