Hello, Lost513, and welcome to Psych Central! I am not sure what to make of this whole thing. Yes, you did continue a relationship after he asked you not to, but I think it was wrong of him to have a fling with a lady you considered to be your friend. And sleeping pills, of all things!

I honestly think I would move on. You don't trust him any more, and he doesn't trust you. You might ask him to go to counseling with you, though, and if he won't go, then go yourself. That's my take on it, anyway.