Standing for your marriage is not for the faint of heart. You will receive the best advice here. The more open and honest you can be about yourself, the better.
First of all, I would not confront your W about the OM, at least for now. You can always choose to play that card later. Once it's been played, it can't be un-played, and you lose the choice.
Depending on your sitch, especially if it turns out to be MLC, any attention or energy given to the OM/OW is not likely to produce a desired result of her "waking up" and seeing the error of her ways. Even worse, it can send her running deeper toward that person, since in her mind, you aren't hearing her. Thus, tightening their bond.
Relationships based on lies and deceit are destined to fail. Let it die it's own natural death.
You are in the company of some very wise people. Have you read DR and DB books? This forum is based on the principles outlined there. You will understand far more after reading those.
