Bf wants Open Relationship?

So I’ve been with my boyfriend for over a year and we both love each more than anything, and for the past few months he would slightly drop hints about what I think of polyamorous relationships/open relationships and I always just said I wouldn’t really want to do that at all because I’m a very jealous and possessive person when it comes to him and our relationship (I’m working on it I know) and I’m just very monogamous, I wouldn’t want to share him with anyone but so now he says he wants to try having a sexual only open relationship because he thinks he might identify as polyamorous.

Hey

Now keep in mind he only wants to hook up with other girls and he wants to try with a transgender woman. But it’s sexual only no strings attached no feelings at all.

So I don’t know what to do about the situation because on one hand I don’t want to do it because just the thought of him with another girl makes me cry and get extremely sad and lowkey angry at the potential future girls he would hook up with but on the other hand if that’s what he wants to try out and if he might identify as that then who am I to stop him? Like I want him to be happy but if I agree to it then I would be sad and angry.

Also if we do it, then it would be a two way street like I would hook up with girls too because I’m bi.

Also he isn’t pushing me to do it or anything he said if I don’t want to do it then we totally don’t have to. I’m considering it because I want him to be happy

I don’t know what to do and I’m feeling pretty fucked up over it Help?