"As in sometimes one sexual encounter in several months time, and an entire year after her pregnancy. During that time, I would make advances and be shot down over and over only to have her tell me that if I really wanted to go and find someone to have sex with, I could, but I should know that I would never have sex with my wife again."
Wow. I would have filed for divorce at that point. Sorry, Homey don't play them games.
And then she comes home and announces she fucked her friend when that sort of thing was an agreed-upon no-no?
I'm going to suggest finding a poly-friendly counselor. I see lots of issues that need to be addressed.
Keep your stick on the ice, man.