for the record, I (27F) have a short lived past with poly/ non monogamous dynamics, so I am pretty familiar with polyamory, and at that point I was pretty open to it. over the years I have become primarily monogamous in my serious relationships. earlier this year I found out a man I was dating for 5 months was cheating on me the entire time. he claimed that he was poly when we met, but when i tried to end things because i identified as monogamous, he said he "would be monogamous" for me because i "met all his needs." (psychotic, i know.) yet he never stopped seeing other people. that entire situation was really traumatizing to me and impacted a lot of the jealousy issues i had worked so hard to resolve.

recently I've been spending time with a man who is in an ENM relationship of 2 months with a woman who also has a partner. we started casually hooking up but it became pretty clear that our connection had a huge potential to be really serious and meaningful. yesterday i had to talk to him about how i got triggered when he mentioned his partner, and that i don't think i can be in a non monogamous relationship based on my recent past of getting cheated on. i'm really bummed out, and we're taking some time apart to reflect on what we should do next (keep it casual/ platonic, stay friends, explore if something serious could work). i'm sad because i almost feel like i would be open for a non monogamous situation with him if he didn't already have a partner, but i just feel my nervous system activate when he mentions her, and i fear this is something i can't unlearn.

TLDR: i was in non monogamous arrangements for a couple years, got more used to monogamy, got cheated on by a poly person who claimed i "met all his needs," and now i am terrified to get involved with a poly person because it triggered a visceral reaction in my nervous system. am i in denial that i am just monogamous???