nycindie, I have told my partner this. He tells me that he wants me to be happy about his other involvements (if/when they happen) and wants to be able to talk to me about them (to a point; I have also expressed that I don't need/want every single detail.)
I feel like we're at a stalemate here. I do believe that time and acclimation will be the only thing for it, but I'm having a hard time right now and kind of dreading a festival that we're going to over the summer; I've never been in that kind of environment with him and am worried about feeling displaced or abandoned. And he seems to feel that much of my reluctance to discuss this means that I don't want him being involved with anyone else. I've never been in a situation like this before, and I'm not really sure how else to deal with it.