Wait as far as I can tell no one's yet mentioned what you're doing. You are willfully being a mistress when the reason you left him is because he cheated on you with the woman he is married to now? Do you see how I dont' understand how you are even in the position you are in? So everyone is calling this man a cheater but you are no less an adulteress too being with a man that you know is cheating. You are not innocent of guilt here either and I don't understand the one sided answers that I've seen here.

Get out of that relationship. Face the fact that you're on the other side of the table now and the mistress and realize that this man, willingly cheats with women, period. Why would you even think it means anything to him? I'm not even sure you understand the implications of the entire love triangle here.