It sounds like you’re dating a guy who’s married, and you want more than an affair. The problem is that he’s committed to his marriage, but you’d like him to divorce his wife, so he can date you in a way that may lead to marriage — right? I’m sure you can tell him without his wife knowing, in any number of different ways from simply telling him straight out, to flirting and being coy with him — but I think that if he wants to leave his wife, he will. Most guys who have affairs don’t leave their wives, although some do.
Tell me a little more about the relationship — your ages, how you met, how the affair began — and if you have any further questions.