Woah Jason... you might want to hold off on cementing this. The door swings both ways and you might be the one to have a discression... if you love her, and it's something that you truly regret, wouldn't you want another chance..?
I've never been in such a situation, but I know a LOT of couples that have and many have stayed together and have better relationships after. Of course if kids are involved that changes things, too.