Sorry, I feel like I wasn't very clear in that last post. My husband doesn't tell me much about his girlfriend, beyond need-to-know stuff; he knows what I'm comfortable (or not) hearing/knowing.
My (male) partner is the one who seems to want a different reaction from me when he's talking about other women. We've discussed this a lot recently; I've explained that I have some insecurities about this, which have only been exacerbated lately by my husband and his girlfriend. He wants me to be able to talk about this stuff with him and "be happy" about it. I feel like I can't right now; I would never expect him not to be interested in other people, but I'm having a hard time with it lately. (We've also been together for nearly a year, and he's been pretty focused on our relationship, to the point that he hasn't really been dating much at all. I think he's fearful of the idea of loss of autonomy, but that doesn't really make sense to me - I don't want him to be with only me, but I also have little to no experience with him being with anyone else, and sometimes new = scary.)
Oh! And a local poly group is a fantastic idea. Thank you.