Sorry to hear that AD. As is typical, she didn't just need to get her head around things....she needed the space to more freely cheat. What a crock. I hope you are angry. Give her space....and yourself space. Detach yourself from this. Go as dark as possible considering your child and work on your life as though you are getting a divorce. Get all your ducks in a row legally and work hard to have custody of your child.
I'm really sorry you find yourself in this position. None of the things I advised above close the door on reconciliation, but it can only happen when/if she gives up OM and decides she wants a life with you again (and you are willing to give her another chance).
You cannot be lonely if you like the person you're alone with. Dr. Wayne Dyer