Anyone experience ending a relationship because you’re not on the same page about boundaries, polycule structure, etc?

My primary partner and I broke up last night; the gist of it is that he wants his secondary partner to be his primary too. She is engaged to someone else but has alluded to the fact the engagement may be ending. He has said that if she is available to be his primary partner, he wants her to be. He has this strong draw to this other woman and really wants to have a kid w her and has admitted that he doesn’t have that same feeling w me.

He wants us both to be his anchor partners; this isnt what him and I originally agreed upon, I know myself and I unfortunately dont think a non-hierarchal structure would be good for me(I have anxious attachment) nor is it what I’m looking for.

What bothers me is it feels like he’s leaving me for the mere possibility of his secondary leaving her primary.

This has been absolutely gut wrenching, I feel gutted I’m extremely sad. I feel like I did the right thing, but I wish he could have handled this differently; it feels as though he didn’t try to find common ground w me.

Anyone go through something similar and have advice? At the very least for getting through this break up. Thanks!