Idk how else to describe the feeling and tbh I think "jealousy" is inadequate

I noticed with my ex that whenever she would get a new partner or speak about a recent sexual encounter I would feel these bags form under my eyes, I would start to look down and it felt like I was dying a painful death inside in the most despairing way. It was always accompanied with a genuine fear response which would leave me irritable, tired and melancholy.

Like genuinely it feels like primal fear and I still haven't found a way to deal with it or even what it is/where it comes from.

I don't know how else to expand upon it and I don't think I've said enough, yet I feel like there is enough I can say.

I really do wanna be poly and feel strange/off put at the though of being monogamous. I was the one who brought it up in the prior relationship in fact, but I have no idea how to actually do this. It doesn't help that I have OCD/severe anxiety and depression along with having been traumatized my whole childhood.

Now I don't feel like I can be secure in any relationship cause of this. I'm confused. The tenants of relationship anarchy, and sexual/romantic freedom is so appealing and makes so much sense that I want to and have tried to do it but I feel like I'm too emotionally immature/childish, and overly anxious to actually manage things like this. I mean my self esteem is kind of non existent either.

Sorry for the rambling, I just dn wat to do really.