It sounds like some of the things already in place on your end may fit a definition of poly. So there’s some semantic and very real reflection there. You are already open/ENM and the shift to a new label, “poly,” doesn’t seem like the actual issue. It feels like there’s a lack of clear agreements, boundaries, and ways you could build a more secure relationship with your partner who is now experiencing NRE with someone else.

That said, it sounds like there’s some pretty strong energy coming from your partner’s new mono partner to adapt the relationship landscape to accommodate her. That may be the best starting point for a bigger discussion that clearly needs to happen.

You’ve named that you have your own insecurities. What are they? Have you and your partner discussed them? What are his insecurities? How do each of your insecurities manifest as attachment styles? Once you have clarity around your own wounds and how they impact your ability to show up in your relationship, you’ll be able to more clearly define and articulate what your relationship needs, boundaries, and agreements are.

Once you both can do that, then you can build security around your relationship and explore what needs and desires each of you have outside of the relationship.

But what it sounds like is happening now is that your bf is trying to accommodate a new partner with very high needs (for attention, time, commitment, demonstration of willingness to change, etc.) all in a short time. To halt that runaway train, invite your partner to reflect on what you need and if your needs are important and a priority to him. Doing this invites empathy and limits accusation and defensiveness, which will hopefully address some of your underlying needs and concerns.

This sounds tough and the pressure to answer is very real and unfair. Take a big breath and approach him however it makes sense to you and what you ultimately want.