It sounds like you don't think counseling is an option and he can't seem to agree to a date or articulate a reason for the delay. Further, he agreed to marry when you came back to him, yet within three days he was backing off. You are hurt, badly disappointed and maybe even a little humiliated.

In thinking about the next step, I am wondering what choice would allow you to have an undivided heart, allow you to accept the ensuing situation through and through.

If you leave, you will be sad, painfully sad. Will you also be able to say that that, though painful, you can accept this choice through and through? Will you be able to say "I can accept that he may never genuinely ask me to marry him and so I'll be alone and/or open to the possibility of other men."?

If you stay, will you be able to accept that choice through and through?

You mentioned that you are feeling resentful of him, used, and understandably so. I'm skeptical that living with him, while harboring (understandable) resentment, is going to improve the prospects of marriage. If anything, it could make them worse. Do you agree?

Would you want to, and be able to, overcome those feelings of resentment? In other words, would you want to say, and be able to say, "I'll live with him and I can accept that he isn't ready to marry and may never be."?

Clarity on the options, visualizing them in your mind beforehand, can help you decide what to do next. I wish you eventual peace in coming to an undivided heart, to a through and through acceptance of a course of action.