Hi, TLDR at the end.

Edit: Also posting this here because I don't think people could relate in other relationship subreddits... Also, we've been together for nearly 6 years now and have been in the lifestyle for 2.

To preface this, it is important to know mine and my partner's understanding of our lifestyle. We engage in threesomes, mostly MFMs together. We've specifically said this is an activity we do together and anything apart from that would be cheating and that we would never be with someone who cheats on their partner.

What happened...

My partner and I were at a bar a few weeks ago with some live music. It was a good show with friends and we all had a good time. After the show ended, I went to the bathroom and when I returned, I was happily surprised to hear the lead singer asked if my partner was single and if he could buy her a drink. She told him she was taken, and that was the end of that. I couldn't imagine much happened since it was just a small bar venue and I was back after just a few minutes.

The next day, she tells me she found his instagram page (not hard due to his band) and I asked her if this is someone she would consider having an MFM in the future with. She said she was interested and reached out to him to see if this would be something he would be interested in. After messaging each other back and forth, we were happy to find out he participates in the swinging community as well and would be very excited to join. We made plans to link up after his next show the following week. At this point, I began asking her to make a group chat so we can all be on the same page, but she never does. This is not normal since we've always made group chats in the past.

Unfortunately, I came down with a nasty cold and was unable to go out the following weekend, so I told her to have a girl's night out and still enjoy the show and get to know the guy a bit better. As the night goes on, they go from one bar to the next. I text her at 2:00 AM letting her know I'm about to fall asleep but to text me if she needs anything. She responds they're grabbing food and should be coming home soon.

Next thing I know, she's coming home at 6:00AM, is excited to see me, has a big smile on her face, and tells me what a great time she had. She was supposed to be getting a ride from her friend (F) which is what I believe happened at this point. I was happy to see how happy she was. She told me a bit about the night, got ready for bed, and that was the end of that. This was the night she cheated on me with him.

Over the course of the next week, she begins talking to me about how she's been starting to want to have casual one night stands and how she never got to experience a "hoe" phase as we like to call it. It really starts to bother me at this point that she has not made a group chat with us yet after repeatedly asking her. She keeps saying she will but never does. Further, we planned to meet up during this week on Saturday and it would start off with her going with him to the botanical gardens in our area, followed by them coming to our house.

At this point, she's asked if she could essentially have a solo session with him before I join them in our bedroom. I'm feeling very uncomfortable at this point with everything going on, how there is no group chat still, and that they're going out on a date without me. Especially with the amount of texting they had been doing back and forth (without me). For whatever reason though, I agree it'll be okay. Come that Saturday though, he bails on her last minute and the night never happens.

That was a breath of relief for me. I told her that he missed his one chance at a solo session with her. I thought that was basically the end of it and that he had cold feet.

Over the next week, I start getting very paranoid about that night she came home so late. I ask her more details about it and that's when I find out he brought her home and not her friend. Her friend had gone over to his house with her and said it was getting late and that they should leave, but my partner didn't want to. This was her final opportunity to make the right decision... but she didn't... Her friend knows what happened but did not tell me which I am also very upset about.

At this point I basically knew she slept with him. I began asking if they fooled around at all and she began lying to me. Then she started saying they just kissed but she told him to stop. I know we're human, and I know if I was in that situation, I think it would have gone on a lot further. I told her I can't imagine how they couldn't have fooled around, but I'll choose to believe it for now.

The next day, I was feeling sick to my stomach. I confronted her one last time and asked her what it was like having sex with him... At this point she burst into tears. She admitted to everything. The lying, and sneaking, the sex. Everything.

I was furious. I couldn't even look at her. I went to my office to be alone and process what she had just told me. I was absolutely disgusted. How could she do this to me? I never thought she'd be capable of something like this. We had LITERALLY just had the conversation about cheating or swinging without each other would result in a break of trust and the relationship and she went ahead and did it.

AND THE FACT SHE WANTED TO SLEEP ALONE WITH HIM IN MY HOUSE?! MY BED?!

I wouldn't look her in the eyes for the next few hours. She couldn't stop crying and saying how stupid she was and how much she regretted her decision.

I've made my fair share of mistakes in the past. I've even told her that I think the relationship should end (big mistake) roughly a year ago due to shifting opinions on whether or not we want kids one day. But we were able to talk it over and figure it out.

I've also made another mistake when we first got into the lifestyle roughly 2 years ago. One that I feel very guilty about, but not nearly as much anymore after what happened. The same way she told this guy that she shouldn't sleep with him, but did anyway (and wanted to do it again very clearly), something similar happened with us. I was particularly horny one day after a night out with her and one of our other male partners in the lifestyle. At the end of the night, we did the same thing that guy did and talked her into having a threesome that night. She ended up saying yes, and we had a great time, but she was very upset with me and our other partner for being pushy about it. Apparently it's okay when a complete stranger does it though.

The night she confessed is also the same night I (mostly) cooled off. I do still love her. I'm even turned on by the idea of her with him and I've communicated that with her. It's the break in trust, feelings of exclusion & not being wanted, and the consistent lying that hurts the most. In her words, she thought she could replicate the night she spent with him, but then I would be included and it would make everything okay. Clearly that didn't happen.

It's been a few weeks since then. I feel much better about everything, but I still don't trust her like I used to. I'm going out of town for a week on business and am scared of what will happen while I'm gone. She's still a student and has several exams next week, but idk.

We've spoken about how in this lifestyle, we are left more susceptible to mistakes and accidents in the sexual space. How tunnel vision can kick in and sex is the only thing on the mind. Similar to other hobbies that can result in injury, except this is in the realm of emotional hurt. Part of the healing has actually been her reciting in great detail exactly how the night played out, down to the exact way he touched her and she touched him while making love together. It has become a very hot scene in the bedroom and I do see myself being okay with broadening our lifestyle. It's a shame it had to occur like this though.

TLDR; Partner hooks up with a guy we just met that we were planning a threesome with behind my back while I was at home sick and continued to lie and leave me out of all conversations with this person when it is not the lifestyle we agreed upon. She even wanted to schedule the actual threesome with him, but go out on a date with him and let him have the first round with her before I joined.

I can forgive her for sleeping with him, but I am having so much trouble accepting the lying and secrets and continuous disregard to include me in the conversations that were being held. I also have trouble with the amount of conscious decisions that were made to leave me out of the loop for so long up to the point of no return. I am still going back and forth in my mind of what to do. For now I have chosen to stay with her and rebuild the relationship, but at times I have feelings of paranoia of it happening again behind my back.

Thoughts? I know this lifestyle is built on trust and consent, but I feel like both my trust and consent were broken.