I'm sorry for what you're going through but I'm glad you're in the right place to start with. First of all, I'm assuming that your W is still living in the house. I am pretty much in the same boat as you are except my WAW ran when she found out she was pregnant and we've been separated for like 8 months until I found out about everything. I won't hijack your thread here so if you're interested, it's probably better for you to go through some of my sitch. Just follow this link Unintentionally testing the waters.
What you have to do for yourself now is to keep yourself busy and do stuff to entertain you make you feel good. If you have access to a therapist, do it. I'm assuming you've read the Divorce Busting book otherwise, I suggest you pickup a copy. Stop snooping since you already know what you need to know.
The question you have to ask yourself is are you at this point willing to take the child and raise the child as your own? When she said the shild could very well be his, do you concur with this? I mean perhaps if you don't mind my saying so, you were not intimate with her at the time the baby was presumably conceived. Otherwise, ask yourself if you're willing to submit to a paternity test. It's amazing how these people get so careless about sex that they have total disregard for what they could be getting from unprotected sex or worse yet getting pregnant. Don't get me wrong the unborn is innocent and had nothing to do with this. It is these two consenting adults who are having illicit encounters with reckless abandon.
As with many husbands in my position, I absolutely have no respect for a man who goes after a married woman. Absolutely nothing. Pardon my french but I think they are SC***BAG!!!!!
There hope that makes you just a lil better. Remember to vent here and not in her presence.
