Associating sexual activity with spouse's girlfriend

Hey all. I've been battling this issue for over two years, and I don't feel I've gotten anywhere.

My spouse is genderfluid (biologically female), came out with it about two and a half years ago, generally swings more male than female, only representing with tight tanks for their their torso and a packer. I'm female and lesbian, have only been romantically and sexually attracted to females. I dated two guys in the stereotypical "Maybe I just haven't found the right one," but when it got toward the intimate side of things, I couldn't bring myself to have sex with them.

Two-ish years ago, they asked for consent to have sex with another woman, whom they wanted to have as a girlfriend (herein "Girl"). We had only been mutually monogamous up until that point, so it was quite a shock and is still a big issue I've been struggling with ever since. We've realized there's been a lot of miscommunication ever since that day, but initially it was because they felt they could be themselves around Girl, and because Girl was ok having a strap-on used on her. Girl's husband had already consented to such a relationship. My spouse had brought up a strap-on from time to time with me, but never as part of their identity. I remember asking twice point blank whether they wanted one for our bedroom activity, and they had said no. Later they had said their reasoning was because my interest in it was only to please them, that I wasn't attracted to the idea/act.

My main issue is that any time I think about them using a strap-on on me, I wig out because that's what they do with Girl, and I don't want to slowly turn into Girl in their mind. And I wish I could get that out of my head. I've bought them the equipment to use with us, thinking I could get used to it, but I haven't been able to bring myself to. It hurts to think they're really only sexually aroused when there's a penis in the bedroom. It'd be one thing if we were using it as a toy, but in their mind, it's physically real.

I'm hesitant currently to suggest any movement because a history of sexual abuse in their past recently came to light. They've often been underestimated and written off by males because they're female, and part of me can't shake the thought that they like the penis idea so much because they're proving to their abusers that they can do it better. They're currently seeing a therapist, and we were seeing a couples' counselor prior to quarantine. I'm thinking I should see a sex therapist, but again--not sure if I should because of the abuse factor could be causing some or any of this.

My biggest fear is that we're sexually incompatible and that could drive us apart, despite that we're on the same page for 85% of our outlook, philosophy, likes, inspirations.

Hello corinth: Thank you for sharing your concern here on PC. I don't believe there is anything I can offer with regard to the situation you describe. (Hopefully there will be other PC members who will have some thoughts they can share.) However I noticed this is your first post. So I thought I would at least leave a brief reply welcoming you to Psych Central. I hope you find PC to be of benefit.