Me and my partner have been ENM since we got together, which was about 2 years ago. I proposed it, as at the time I really enjoyed casual sex with women and he with men (we're both bi), and I thought keeping these doors open would be satisfying for both of us. When we were discussing it for the first time, I really didn't think about it enough - I just blurted out that "I'm happy for you to sleep with whoever has a dick - it's something I can't give you". We're long distance and were going to let each other know if we were going to see anyone, just to keep safe, and I also found it arousing. Overall our relationship is really wonderful, we are very committed to each other, and he works overtime every week to get extra time to travel up for 6 hours to see me. We don't really fight and our sex life is very good.

Fast forward few months, he texted me to say he was out to meet someone. A few hours later I asked him whether the guy was nice, to which he replied "It was actually a trans woman, she was very nice". It absolutely pulled the rug from underneath my feet. I don't know why I hadn't thought about it before, but in that moment it felt like he just had sex with a woman, which I wasn't comfortable with - the trans woman in question was pre-transition, so they had sex like he would with anyone else off Grindr, but it left me feeling betrayed - he went out with a woman and slept with her. I told him that I don't want him to do that anymore, and he promised he wouldn't. After that, on a few occasions, I told him that I might reconsider that, I just don't know how I feel yet. A few days ago he was trying to show me a screenshot of something, and in there there was a photo of them together in a club. I asked him why he had such a recent picture of them together, and he showed me their conversation on Grindr. Apart from the initial conversation a year ago, she sent him a photo that popped up as the Google Photos memory, and asked him out again several times. He refused every time, but didn't tell her that he had a partner, or that we had an arrangement. He just made excused for a good month. When I asked him why he didn't just tell her, he said that he didn't want to block her instantly since I told him that I might reconsider my stance on that, and that it was just easier to make up excuses, since she only visits his city once or twice a year. I feel extremely hurt by all this, when I asked him why he took a screenshot he said that it was stupid, but he just wanted to have it as a memory, since it was the only trans person he slept with, and he considers himself really lucky, because they are very attractive to him. He said he hasn't spoken to any other trans woman since and he's not going to because our relationship is the most important thing for him. I feel horrendously hurt, and confused about who's in the wrong here. I want to support trans women's desire to be treated like women, but from what I've learned from my other queer friends, this often doesn't translate into the bedroom. It also somehow feels like a betrayal that he took that screenshot. I don't know what to do or how I'm supposed to approach this.