"... possessive boyfriend ... [he] doesn't want to breakup."
The thing is, a relationship is about two people. It takes both to be together, but one to break it up. You no longer want to be in the relationship. He doesn't like it, so too bad. I hate being harsh, and I've been on the losing end of that before. But them's the breaks, so to speak. My current girlfriend and I had that conversation a long time ago.
"my husband and the woman he is cheating with"
I have bad news for you, sexya: Unless he changes himself, he will either continue to cheat, or cheat again if the right circumstances arise. Nothing you can do will change him. Going against someone's free will is not such a great idea. Sometimes it's just time, even if it's difficult. Divorce papers can sometimes do the trick, however.