So sorry you are here, but I have to agree with the others, you deserve someone who will treat you like you are the only woman on this earth.
This man is not the person you thought he was. He is a cheater, he refuses to discuss it or give you the details, and has done nothing to work on himself.
Yes, his affairs can go underground. There are other ways to cheat, a monthly payphone, different email accounts, calls from his work phone, lunch hours, etc.
Please think long and hard about a future with this man.