True2Self--I will say that the fact that we are all being open and honest now is a HUGE factor for me in this. I've told both my husband and his girlfriend that honesty and openness is the most important thing to me right now and any signs of things going on behind my back are going to make me close right up and feel like this is never going to work.
The one thing I've become very clear about is that I don't want or need lies in my life. I expend too much energy on trying to uncover what's going on, feeling bad about myself, etc. and that's just not how I want to live. I can deal with just about anything if I know the truth.
I also feel like this is something where I have the right to make a choice. If I want to open up my relationship, then that's fine. But cheating is just a way of opening up a relationship without the knowledge of both parties and that's really disrespectful and unfair.