How do I get my committed guy to stop talking about other girls?

Alright, so I’ve been with this guy for almost a year now. And things are great. But, continually he talks about other girls, its always been look and no touch… and I’ve been fine with that. Let him have his fun, and as long as at the end of the day he’s still all mine I’m happy as a bumblybee. But, lately the stories of pre-me have gotten raunchier and raunchier. I’ve tried asking him not to tell me, but then… I want to know if he’s making such a big deal out of it. there’s this one girl he met before i came along, and he had a threesome type thing (not full on sex, but pretty close) and he says she “gets him”, understands him when he says things, had the same experiences and viewpoints as him. shes going to be up in his cottage area thanksgiving weekend, and he’s sad because they’ll only be able to talk. he wouldnt cheat, but he whines about not being able to have sex with her, grope, kiss any of that stuff. I suggested me coming up as well and us all fooling around together, in case maybe hes getting bored. hell, what guy wouldnt go for a threesome? but he said no, it was just wrong. and said he wouldnt, cuz he liked me better. i don’t want to break up with him, but how do i talk about this and/or get him to drop this “other girls” thing?