Throwaway because I know some IRL friends are in this subreddit. Long story, but my head's a mess right now and I don't know what to think.

I (F31) have been happily in a poly relationship for the last three years. My long-distance partner, Nick (M36), has three other partners, two of whom he lives with. I see Nick every 2 - 3 months and stay with him and his two nesting partners for about a week every time. We all get along splendidly. In the meantime, I've been on a few dates with folks who live closer to me, but nothing has really clicked.

Back in October, I attended a weekend social event with Nick and his other partners. It was very fun, and I made lots of new friends. One of the friends I made was Martin (35M) and we had instant chemistry. I certainly noticed him almost immediately, and our first interaction was very much a "meet cute." Wanting to scope things out and see if I had a chance, I asked one of my metas who had known Martin longer, and she let me know that he was married and monogamous, with several kids. I was mildly bummed out, but flipped the switch in my brain from "potential romance" to "potential friend" and moved on with that in mind.

Over the next few months, I wound up occasionally seeing the friends I made at this event, usually in larger group settings. Martin and I wound up slowly becoming friends. On social media, we would send each other the occasional meme and chat casually about our daily lives. At one point he paused the conversation for a, "Hey, you're great, I just want to be clear neither of us is looking for romance, and if you ever feel I've crossed a line, please tell me" conversation, which I really appreciated. His kids are adorable and I also really got along his wife. I wound up dropping my guard a bit. I have a few other platonic guy friends, but always held myself at a bit of a distance from them. In this situation, however, I guess I felt like the fact that he was married with kids was "safer" and I wound up chatting with him regularly and opening up about more vulnerable topics. (To clarify, by "vulnerable", I don't mean in any way inappropriate; mostly childhood stuff, relationship with my parents and siblings, etc. 100% the conversation never became romantic or sexual in nature.)

I admit I still had a bit of that initial attraction to him, and would get a bit more excited to see a message from him pop up than from one of my other friends, but I tend to catch feelings easily, and told myself it would pass given time and familiarity. I was also happy to see that Martin and Nick were becoming good friends and that the two of them enjoyed hanging out when I would go to stay with Nick. I felt like my friend circle was expanding. Everything was comfortable and fun.

I guess I was naive.

For the last couple of weeks, Martin's been ~jokingly~ saying things like, "Aw, you're so cute when you do [x]", "you're my not-girlfriend", "don't make me fall in love with you", etc. I noticed it of course, but I also joke around with a couple of my other platonic friends with way, so I tried not to give it any undue weight, thinking if I was reading anything more than joking into it, it was just because I still had some mild feelings for him.

Last night I was enjoying a watch party with Nick, his nesting partners, and Martin. About an hours into the evening, Nick and NPs got a visit from a neighbor and hopped off for the evening. Martin and I continued watching stuff and chatting. I noticed that he was drinking quite a bit, but didn't really think much of it. His wife also filtered in and out of the room he was in and said hi. I had a brief chat with her, but she was busy with her own tasks and didn't really stay for long.

The topic somehow circles around to a small argument Martin had had with Nick the week prior, and he said something that really caught me off-guard. "I think you're too good for him and you deserve better. I'm probably saying that because I have a crush on you."

I was shocked but got out a reply to the effect of, "I love Nick, I think he's too good for me, and also you're married..." to which he replied, "I know, nothing's ever going to happen with the two of us. I've got it under control."

His wife popped into the room at that point, and he turned to her to explain, "Yeah, I just had the conversation with OP about the crush I have on her" and his wife shrugged, barely acknowledged it, and asked him a question about household stuff before stepping out again. (Honestly, I feel a bit relieved about this; at least he's not hiding shit from her?) I made a quick excuse and ended the video call.

This morning I'm feeling... absolutely awful. I feel like an asshole for pursuing a friendship with a married man whom I had feelings for. And I feel stupid for thinking it *could* just be a platonic friendship. One of the friends I've told pointed out "a married man doesn't just start up a friendship with a poly woman" and I guess that's true and I'm at fault for not seeing it, or I ignored it because of my own little crush made me just want this friendship more than I should have. And I feel a bit betrayed. I really did think we could just be friends. I never, NEVER would have crossed any kind of line with him. I expected to just wait out my own feelings until they faded. Now I feel like that's impossible because there's always going to be this weird barrier here, and it just killed the possibility of future friendship because I'll always have my guard up. And most of all I'm really pissed about what he said about my relationship with Nick; I honestly thought they were friends, and it feels like a double betrayal that he would say something so negative about Nick behind his back.

My head's just a mess right now and I need some clarity from objective parties. I'm pretty sure I need to just block and move on. There's no good outcome to maintaining this relationship, is there? At the same time, we're in the same social circle, and unless I want to remove myself from that friend group completely, I'm 100% certain we're going to run into each other in the future. I don't know what my next step needs to be or how I can get past this. I just want to kick myself for being so naive.