@onthefence2511,
When your husband cheated on you, I'm guessing you had a few choice words for him and for the person with whom he cheated. Maybe you called your husband a bastard for cheating. If so, consider this. You are now involved with a bastard. Why would you want to be involved with a cheating bastard?
I made a point to someone else on here in exactly your situation. The reason she doesn't care about sleeping with another woman's husband (again, even though she probably hated her husband cheating on her) is because she doesn't give a damn as long as she gets what she wants. If this is how you feel, then there is not much advice to give.
Anyway, if you are happy being the other woman, and doing to some other woman what you had done to you, then fine. But remember, if he is willing to cheat on her with you, then he could and probably will cheat on you with someone else. Heck, maybe you are just one of a couple of women he is fooling around with behind his wife's back. Just something to think about.
I think you know what you should do. You don't need advice as much as the confirmation that ending it is the right way to go. Consider my as confirming that you should walk away permanently from him.