Sorry, this is a long one.. I've needed to put this down in writing for a while and I guess now is the time since this saga is coming to an end..

I (M41) met my girlfriend (F37) about a year ago.. I was stuck in a long term dead bedroom situation where my wife told me to find someone else to fuck, and she was being pushed to date by her husband to satisfy his hotwife fetish. We hit it off immediately, and made plans to meet up at a hotel soon after. I couldn't actually get it up so instead we just hung out for a while and it became clear that we really clicked.

My marriage kinda blew up after that. My supposedly asexual wife got upset and said she wouldn't do one-sided ENM, so she declared she was poly and was fucking her new boyfriend by their 2nd date. We eventually separated, but that's a story for a different day..

Anyway, I met with my not-yet-girlfiend a second time at her house, and this time her husband was there and wanted to watch. Once again I couldn't get it up, but we did stuff and it seemed everyone was happy. They both invited me to keep coming over. A bit of drama occurred in the meantime with my wife, but eventually I came over for a third time and was kinda pressured into a threesome without adequate time to prepare for it. It was fine, but at this point I was really crushing hard and confessed that I was starting to get feelings. This kinda didn't land well and I went home thinking I'd probably never see her again. Later we texted a bit and she told me that if they were going to deal with feelings they wanted a unicorn to date both of them. Being hetero, I said I couldn't do that and we broke up for a while.

I found a few dates after that, but kept in touch over text. She would ask how my dates were going, and I would ask if they bagged a unicorn yet. Eventually she told me she and her husband had discussed it.. He asked if she could love 2 men, she said she could (though she didn't tell me this until later -- neither of us had said the L word yet). We were back on.

Things happened quickly after that. We went on dates, became officially boyfriend/girlfriend, said our "I love you"'s and everything was great. She even met my kids. Her husband was supportive up through this and said it was cute that we loved each other. Then, one night when I was at her house, after her husband had watched us for one round, we decided to go again.. We apparently had a little too much fun. He got weird, she got sad, and I left early.

Ever since that time, things have been off with him. He would one day be cool with everything, then the next would freak out and wouldn't let her hang out with me. She and I planned a beach trip, and he said to me that it was fine, but later tried to prevent her from going on it. Every time she wanted to spend time with me became a struggle.

He did start dating and for a while it seemed like things were getting better. He let me and my gf spend time together, have overnights, etc. without a lot of drama. Then some shit happened with the girl he was dating and he started acting out again.

About a month or so ago her gave her an ultimatum: it was me or him. She struggled with it and eventually when he realized she might leave him, he called me up, apologized for doing this, and asked me to help walk it back. And so I did. I had previously considered him a friend and was willing to go back to us all being cool with each other. They got a marriage counselor, and I was happy to hear things were improving between them. I thought everything was good.

Welll, last week I learn that apparently he's back on the ultimatum. She has to choose if she wants to blow up her life to be with me. I feel fucking betrayed after helping him save his godamned marriage. And this time I told my girlfriend that she can come live with me if she wants. We can be mono together, or poly, or something else. As long as I have her in my life. It would be a challenge and we'd have to figure some things out (I have shared custody of my kids), but it would be worth it to have a life with her.

I was fine sharing her, even though I personally lean towards monogamy. I didn't even mind the occasional threesomes, even though that's definitely not my thing. Girlfriend and I both did everything we possibly could to make sure her husband was getting what he asked for out of the deal. And now I might lose her because of a dude who invited this into his life, cultivated it, and then decided his feelings were more important than everyone else involved and went back on everything he agreed to. And I'm devastated that I might lose out on the best relationship I've ever had.

I don't want her to have to choose, but if she has to choose I want her to choose me. And this all just fucking sucks.

Edit: changed some working to be a bit more fair to my meta.