@Ari4,
You're stressed (hence the nausea, etc.). And you aren't exactly getting great assurances from this guy.
He is certainly entitled to have female friends (don't try to control who's friends with whom - ever. That way lies madness and is awfully controlling). But he's saying one thing and doing another.
"Kurt (or whatever his name is), why are you still in touch with Stacey (or whatever her name is)? Didn't she drive you up a wall when you were together?"
And he answers, "But I miss her!"
And then you ask something like, "What are you missing?"
And if it's something in your relationship, well, it's up to you if you decide to provide it or to change. If it's just that he was friends with her for a long time, then I'd personally be inclined to give him a pass, at least the first time.
But listen to what he's really saying. 'Cause if he misses his orgies and his adoring fans, and you're in the way of that, I'd suggest to you that he will find a way to get those things back - whether or not he decides to stay with you.