Partner confided in his ex girlfriend about our sex life

My partner and I have been together for just over a year. We’re in our 30’s and met through friends. We don’t live together yet, we see each other a few nights a week. We’re in love and have started planning our future together.

A few months into dating he admitted to me that he was still friends with his ex and she had called him that week. They met at school but didn’t speak for years until their 20’s. He said he wasn’t interested in her romantically but she made it obvious that she was and would sneak into his flat and lay rose petals on the bed, get into sexy lingerie etc. and eventually she wore him down and they dated romantically for a year. He says he broke up with her as she was planning to go travelling and he didn’t want to do long distance.

She moved halfway across the world (24 hour+ flight) and still lives there. It’s been 7 years since they split up but she came to visit him 3 years ago (according to him nothing sexual happened). During that time they have remained friends. They have both since had other partners.

He told me that she checks in with him every few months and that was the extent of it. I wasn’t overjoyed to find this out but I trust him and was pleased that he was honest about it.

Fast forward to a week ago. We went away for the weekend and ended up having a falling out, basically he misheard something I said during sex and was clearly upset with me the next day but wouldn’t tell me what it is was as he didn’t want to ruin our weekend away.

When we came home he acted distant for a few days but arranged to come over to mine to talk. When he finally told me what he heard, it was completely wrong, he thought I’d called him by an ex’s name when I had said something entirely different.

He was so relieved and admitted he had reached out to one of his girl friends for advice on it. Immediately I questioned whether it was his ex girlfriend and he admitted it was. The irony! Apparently she had taken his side and agreed that I must have said my ex’s name if that’s what he heard and that’s why he had been acting distant with me.

I was shocked and upset that he had discussed personal details of our sex life with his ex girlfriend. He said that was the type of relationship that they had and they were comfortable talking about their current relationships including their sex lives with each other. He got his phone out and showed me the messages without me asking but tbh I didn’t want to read them as I was too upset.

I made it clear that this made me feel extremely uncomfortable and discussing personal issues with an ex is emotional cheating in my eyes and crossed a boundary of mine. I asked him never to speak about our relationship with his ex again or anything sexual for that matter. He agreed and offered to stop speaking to her entirely but I said I wouldn’t tell him who he can and can’t talk to but I suggested he set some firm boundaries with her.

I’ve since done some digging and worked out that she’s the same girl who posted on his Facebook wall for his birthday around the time we got together. He turns off his birthday posts so hers is the only one there so she must remember the date. This message could have easily been from a girlfriend, love hearts, telling him she misses him etc. I’ve scrolled back further and seen that she had done this every year since they split until this year, sometimes with photos of them when they were a couple. She didn’t do it this year perhaps because I’m in the picture? Or maybe she did and he hid it. Who knows but I feel like these posts are her marking her territory, always mentioning how they met at school and how much she loves him and misses him. I’ve also noticed comments on his profile pics from her, for example “I forgot how sexy you are”. I’m getting strong pick me girl vibes from her Facebook activity and from what he’s told me.

I don’t think there’s anything more I can say to him on the matter, I’ve told him how upset I am and that I want him to set firmer boundaries with her. He has also apologised sincerely and admitted that his actions were disrespectful towards me. I’m aware I can’t force him to do anything so all I can do is trust he does the right thing (he hasn’t ever given me a reason not to trust him until now) but I can’t stop feeling insecure about their friendship.

Any advice or wisdom?

TLDR: Partner confided in his ex girlfriend about our sex life, I’ve since found out they still have a close emotional relationship.