I'm going through a similiar situation now...WAS with OM. My MC said to calmly confront my W and let her know that I know about the A (I did, but she is still denying it). Then MC said to go dark and back off completely. She said the A will most likely continue, but I will have burst the bubble and the A will burn out eventually (might be 6 months, might be sooner). She said then it would be up to my W to make contact if she wanted to express regret and work on our marriage AND it would be up to me if I wanted that.
One key thing she said - you can not force someone to end an affair. That only makes it more exciting and they will just carry it on behind your back.
You are now in the driver's seat. So act like it. Get a life, reconnect with your friends, take care of yourself, exercise, take up a new hobby. You can only control one person - yourself. I don't know if you are legally separated, but in most states, you have to be separated for 12 months. So nothing is going to happen now. Slow down, take a deep breath. Time is your ally.
