How do you deal with your ex-boyfriends' new girlfriend?

Here's the situation, My ex dumped me for another girl back in March and despite the fact that he accidently told me that he slept over at his new girlfriends house 3 weeks after he dumped me (which indicates sex) and he apologized for it. We're still friends with benefits..our relationship is a little weird. But anyways, he invited me with a group of his pals to see a play and spend the weekend with him...and his girlfriend. This is his 3rd girlfriend that hes had since march and they've been best friends for years now and closer to his age. The problem is, I still like him and I lied to him when I stated that I was seeing someone just to bust his chops even though he's not the jealous type. I told him I'd be pissed off if I felt like the 3rd wheel when I see them next, he understood. How should I deal with him and his new girlfriend holding hands and kissing while i'm out with him? I told him I don't want to see that, hell act as if they aren't a couple. How should I manage to get some time alone with him considering she sees him all the time and I haven't seen him since July (last time we hung out as just friends)? Especially since i'm staying over at his house that weekend and I don't want her there at the house, how should I tell him that? I know there's a possibility I may never get back together with him (since we did that 2x). Even the thought of him with another girl makes me uncomfortable. Plus she's better for him than I am considering they've known each other longer than I have, I can't even compete with her (with low self esteem). I need someone to address all of my points here on this one please?How do you deal with your ex-boyfriends' new girlfriend?
OK, this situation is just too weird. I don't have a clue.








I got an idea, QUIT SLEEPING WITH HIM! He has a girlfriend now.