I think I might have missed something here--I read that he was kissing her, and then I read that you're concerned that she may be pregnant? So there was a little more than "kissing" going on?
I'm going to suggest that maybe you'd like to come visit over in the "Family and Friends" section of the forum. It's here
Friends and Family of Alcoholics - SoberRecovery : Alcoholism Drug Addiction Help and Information
If you use the "Search This Forum" button (immediately above list of threads, towards the righthand side) and the search term "blackout" or "cheating", you'll find many posts/threads that are more directly related to your situation over in that section.
An example would be this one:
http://www.soberrecovery.com/forums/...d-cheated.html
Hope you continue to read and post, wherever you choose to do it.