My primary partner is currently on a date (at least, I think it’s a date) with his ex Ellis (pseudonym), and I’m feeling anxious about it. I just came back from a three-week work trip to another continent, and though we spent a very nice evening together yesterday, and I received a lot of love and care from him, I feel a bit hurt that he’s with her now, right after I just landed. It feels especially painful since, in the past, when we were 'just dating', he “chose” this person over me and distanced himself to be with her. What he then said about her still lingers in my memory: "but Kaleido, what I feel for Ellis, I have never felt something like that before".

Ellis also used to struggle with significant mental health issues (BPD), which makes the situation feel more complicated for me. He told me he sometimes checks in with her to make sure she’s doing okay. While I find that very caring and admirable of him, I worry that she’ll come to see him as an anchor again—or someone to receive care from—which could lead to him distancing himself from me again or even to our relationship ending.

I feel like I need reassurance from him when this date (?) is over, but I’m unsure how to ask for it without sounding jealous or needy. I also don’t know if he understands that this is a bit difficult for me. We had a miscommunication about my arrival date, and when he mentioned he had planned this evening with her, I immediately said, “just keep it like that; you haven’t seen her for so long,” without him even offering to change plans. But deep down, I felt - and feel - quite a bit of fear around this.

How should I approach this? Should I not mention it at all and just wait and see what the future brings? We are planning on moving in together. But what if he, for the second time, decides that she should be his primary?

*Edit: added pseudonym for readability.