This is interesting, because it sounds a lot like the relationship I was just in.
What do you want, exactly? Marriage? Verbal commitment? To be "official?" It sounds like you're already committed to each other, even if it's not "official."
Do you want to be with him, or do you want to own him?
I don't understand why, if you're committed already, you need some kind of verbal confirmation. Why is it that you can't enjoy the relationship for what it is?
AMF's advice is the best response here so far. Someone else also mentioned responsibility. It sounds like he wants to be with you but doesn't want to have to be responsible for you; he wants to remain an individual.
Whether or not this is what he's really thinking, it's clear that he doesn't want to be forced into something more serious. Having a confrontational "we need to talk" conversation will only inspire a fight-or-flight response. Suddenly stopping the sex will have the same effect.
My suggestion, what I would have liked to have seen in my relationship that may have saved it, is that you back off a bit. From your posts, you sound very needy and attached. Don't call him as often, especially if you have nothing significant to say. Don't talk to him every day, don't initiate things as much. Give him some space. Let him have his own life, with you as a part of it, rather than trying to become his life.