Need to Talk

So about a year and a half ago I started talking to a guy who had gotten out of a relationship with a woman who is 15+ years older than him and isn't the nicest person. We got really close but never slept together and he started seeing someone else last summer but that only lasted a few months. We saw each other a few times last winter but nothing more. He started dating his ex last spring and all of his friends were pissed. I'm also good friends with a few of his friends and they told me he talked about me all the time. None of his friends like his girlfriend and they never do anything together. Well we were at the bar together this weekend and one thing lead to another and we ended up back at my house and we had sex. I find out from our mutual friend that him & his girlfriend have an open relationship. I know it probably didn't mean anything to him but all of his friends are hoping this "makes him pull his head out of his ass and break up with that bitch". Their words not mine