Wish I had dodged it, but a general piece of advice for everyone is familiarize yourself well with what a narcissist is, covert, overt, whatever kind, and if you are in a relationship and someone is making you question yourself, telling you something never happened or that you're too sensitive or crazy or whatever or trying to isolate you or tell you that you shouldn't talk about your relationship problems to other people, GTFO. Always have some fuck off money saved and a go bag packed. Learn what grey rocking is until you get someplace safe. They don't change, they don't have insight, but they'll lie their way into convincing you it's all you and what you've done. They're actually incredibly dangerous.
And if someone is pushing you to try polyamory and you don't want to, you're just heading for a split anyway and they are going to cheat anyway. This didn't happen to me but it's such a red flag. If you are both into it, you do you, but it's never a good sign if someone is trying to force you into it.
Finally, don't ever lose control over your finances. This was a big mistake I've made and I'm paying for it. A favourite trick of my narcissist SO was to take my credit card and buy himself a bunch of stuff to upset me when he felt like I wasn't "engaged in the relationship", which meant I was depressed and withdrawn because of the hell he was putting me through.