My partner said he was okay being polyamorous, now he wants to become monogamous and I don't want to

My partner has been lying for three years about being okay with my polyamory. I’ve been in relationships. And every time I’ve asked multiple times. He profusely said he didn’t mind, that he was okay with it. I don’t know if at this point in the relationship I can be monogamous with him. Too many things have happened. What do I do?

If I wanted to move to Scotland, and my partner said he was totally fine with it, and we talked it out and he said he did want to go, and we moved to Scotland, and I spent 3 years building a career, making friends, putting my home together, all with the assumption that it was indefinite if not permanent - and then 3 years later he said he didn’t actually want to live in Scotland, I’d help him buy a one way ticket back to the US.

Now, if he told me “I thought it would be fun, I thought I would like it, and I had every intention of staying here, but after giving it 3 years of a good college try, I’m just not happy here and I need to act on that information” - I’d be sad, but I couldn’t be angry that he wasn’t able to predict the future 3 years ago. He said yes in good faith, but now he’s tried it out, and the point of trying things is to see if they work for us. I can’t ask him to be dishonest with himself and with me once he figures out that Scotland isn’t working. But, if it came out that he never wanted to do it, and knew the whole time that it wasn’t going to work out, and had knowingly lied every time we discussed it and let me build a life and envision a future on what he knew was shaky ground, I’d be PISSED.

So I just want to make sure your use of "the word “lying” here is accurate. Saying something he thought was true at the time but turned out to be false is not “lying,” just like when I tell my kid that we’re going out for poke but his favorite poke place turns out to be closed, I wasn’t lying, I was just wrong. If he’s just now figuring things out, it’s not his fault, and it did take some courage to tell you, so while it’s definitely a sad thing, he didn’t do anything wrong. But if he was being disingenuous with you and knowingly letting you act on information he knew was false, that’s not okay.

But either way, the fact remains that he doesn’t want to stay with you in a polyamorous arrangement, and you don’t want to stay with him in a monogamous relationship, so it doesn’t sound like things are going to work out. I don’t mean to be flippant - a 3+ year long partnership is a tough thing to dissolve - but this sounds like his problem, not yours. He made a choice to try this out, now it’s not working for him, so he doesn’t need to keep doing it. You’re not obligated to become monogamous with him if that’s all he wants; he’s not obligated to stay polyamorous with you if he doesn’t want to. It’s okay to grieve the loss of this relationship, and to be angry with him if it’s his crappy choices that have brought you to this point.