I'm a polyamorous person. My now ex boyfriend is not. When we started dating I explained to him what polyamory was and I straight out said, "I understand that you're monogamous and so if you can't handle me being in a polyamorous relationship, I can handle being in a monogamous one because I love you." He said TO ME, "No, it's okay. I love you, and I understand that you still love me even if you also love other people. We can be in a polyamorous relationship." I then said, "If anything ever happens with another person, I'll tell you immediately and if it makes you uncomfortable I'll never do it again." And he said it was fine. And nothing happened for over a year, but then one night I had sex with another man. And just like I promised, I told him, and at first he took it well and he was like, "I understand, I still love you. Everything's fine." But then a few hours later he freaked out and said I cheated on him and that he can't handle it and then he dumped me. Why? Why would he lie to me and tell me it was okay when I didn't even ask and then dump me and break my heart when we were supposed to just talk... He did so much to me, and caused me so much unforgivable pain that I managed to put up with for nearly two years, but one instance of something I didn't even do wrong and he destroys me...