Dear wife59,
Ideally, you would leave him, royally screw him in the divorce, and perhaps completely damage his reputation in whatever town you live in? Unfortunately, I would honestly have trouble telling you to do this (because I've stayed with a cheater), and because some of what I've said is not so nice.
I cannot imagine how you must be feeling right now. I really am so sorry that this is happening to you. I'm sure a lot of people would disagree with me on this, but I feel that cheating takes a toll on men and women in different ways.
Not to say that one sex takes the blows particularly worse than the other, but it just seems like cheating basically damages a man's pride, while it destroys a woman's self-esteem, sense of purpose, etc, etc.
Therefore, I am quite unsure of the best advice to give. The one thing I do know is that you DO NOT deserve this. You must remind yourself of this constantly, no matter how long he continues to see these women, and no matter how long you're willing to endure it.
Stay angry at him - don't turn that anger toward yourself!
Maybe you two could see a marriage counselor? I've heard that having a third-party intervene is one of the easiest ways to get people to see the error of their ways (because they will obviously think any advice from the other partner is biased).
Also, I would say not to have sex with him again, but any psycho-sexual advocate would say this could have caused the problem in the first place.
Maybe you should try to focus on you. Get yourself healthy. Get your self-esteem back. Find new friends. Find a life outside of him that you enjoy. At the same time, talk to a counselor and if he won't change his behavior, get to the point where you have mentally/emotionally prepared yourself to leave him, and get out!
Sorry if my advice/reply seemed a little scattered. I always take the all over the map approach with advice. But yes, let me know what you think.
Best of luck and love to you. I am really wishing you the best and hope to hear something positive back!