A bit of background: My relationship with my partner Aspen started out as a mono-poly arrangement, (Aspen had a few other partners when we started dating), but recently I've started seeing Birch and Aspen had a lot of trouble dealing with it. We had restrictions, we got rid of them, and now there's no limits on what sort of activities Birch and I can engage in.

I feel like I'm the only one not on board with my sexual relationship with Birch progressing further and it's making me quite frustrated with myself.

The first time I engaged sexually with Birch (not actually having sex, just publicly inappropriate kissing and touching and whatnot), Aspen had a very big, very upset reaction to it. I knew Aspen was really struggling with jealousy, and I had been trying to be gentle and supportive working them through it, but it was a much bigger reaction than I was expecting. Almost immediately afterwards (less than 4 hours, really) after working through all their big emotions, Aspen is now completely 100% on board with me having sex with Birch on our next date. They're excited for me to do so, they want to talk about my upcoming dates, they keep asking me if I'm excited, etc. I know part of this is because Aspen has a kink for this sort of thing, and I've been happy to talk about it theoretically before.

Important note: I don't plan to share sexual information about Birch with Aspen, that's a consent violation and I'm not comfortable with that.

Birch is also very excited to be more sexual with me in the future. They had a very good time on our last date, and were hoping things would go further, but they were very understanding of my boundaries and I didn't feel pressured by them at all. They're very excited for our next date, and while they don't expect to have sex, they haven't been shy about telling me they've been hoping for it for a while.

Unfortunately, I'm not nearly as on board with it as Aspen and Birch are. There are some shallow, personal things that are dampening my excitement (I absolutely hate smelling Birch on me/in my house after a date. They're a great person, and they're attractive, I just really don't like the way they smell), but Aspen's initial reaction definitely has something to do with my reluctance. I just don't know how much of my reluctance is a misplaced desire to avoid hurting Aspen, and how much of it (if any) is genuine "I don't actually want to have sex with this person right now" reluctance.

I feel like it wouldn't be fair to Birch if I avoid doing things with them because I'm worried about how Aspen might react. It would also make Aspen very sad if I didn't get to do something I might enjoy because of their reaction to it. But every time I think about having sex with Birch I get uncomfortable, and I'm not sure how to move past that. I'm also worried it's not fair to myself to have sex with Birch when I'm feeling so reluctant. But of course, if I avoid doing so, I run the risk of being unfair to both Birch and Aspen. It's a difficult situation and I'm frustrated with myself.