Please tell me how to handle this weekend knowing he is going of the see the OW. I am letting my emotions run away with themselves and I am getting that deep pit in my stomach and burning in my chest. What do I do?
K,
I think you should look him square in the eye and say "I certainly hope you're not going to visit your girlfriend, and lying to me about it. Because I would find out easily enough, and that would be incredibly disrespectful to me, to our marriage, and to our family. I think I deserve the truth, don't you?"
And then see what he says.
If he lies to your face, and you KNOW FOR A FACT he's lying, just shake your head and walk away, or say "Stop it. We both know you're lying to me right now, and it's incredibly disrespectful. If you want to have an affair, I can't stop you, but I do insist that you be honest with me, as we've always taught (S6) that families shouldn't lie to one another."
Don't raise your voice, don't make a scene -- just state it very matter-of-factly and while making eye contact with him.
You don't need to beat him over the head with his affair daily, but you don't have to pretend like you're oblivious, either. In fact, you shouldn't.