Most of us feel this way. It is the result of triangulation, and EXACTLY the way they want us to react. You were not possessive. You were reacting to someone shoving their emotional cheating in your face & darling you to leave them, knowing you wouldn’t. She wanted to see how much you’d suffer, just to get the privilege of continuing to be abused. The fact that you are trying to figure out anything that you could have done “wrong” speaks volumes to your character. I have to admit yours is the first male post I’ve ever even read past the revelation that it’s a man writing it. I guess this experience is so much like mine that I wanted to send you support. I am so glad you are away from her. It’ll take time but your life is going to be 1000 times better soon. You are a good man & those are in short supply.