Jenn,

I agree with Ange1961, protect yourself first.

His cheating only reflects on himself, not who you are as a person. He is going outside the marriage for some screwed up reason in his head. Something is justifying it to him. And cheating is putting emotional energy into another relationship, it doesn't have to be consummated to be cheating. He is taking the energy he should be using to become closer to you, and using it to become closer to some random woman he found on the street. So don't feel bad for being ANGRY you have every right to be angry, he is giving away your time your love.

Sometimes, they need to have the repercussions of their actions. Only you can judge, we walk a very fine tightrope. Do I push on this, or do I let it go, if I push on this, does it push him over the edge and I walk away from it guilty the rest of my life?
We tend to just let SO much go because we are afraid that standing up for ourselves will cause that last final thing and drive them to the ultimate out.

But NO one deserves to be cheated on. You have a right to protect yourself and your life. I wish I had better advice. I feel for you.