u/Ventilator-4

I’m (26F) struggling quite a lot with the person I’m dating (28F) and I could really use some outside perspective, especially from people who have experience with poly/open relationships.

We met through a mutual friend and immediately hit it off. We saw each other a few more times through that friend, and eventually she invited me over because she wanted to spend time with me. She then told me about her Dom (36?M) who she was already involved with and explained that they meet once a week or less and talk about what scenarios they’re going to do. She said he’s not involved in her daily life.

We started hanging out more and things were really fun. After a while, she told me she saw us as dating, rather than just a situationship. We talked about what we wanted from relationships, and she said that ideally she would eventually like something somewhat open once she was in a secure relationship. She still wanted to go to fetish events and continue doing rope, etc.
I was actually excited about this. I’ve always wanted to explore my sexuality more, but I’ve never really been in a relationship where I felt safe enough to do that, and I’ve never had the confidence to explore those things on my own.

Then, after about two months of what she called dating, she suddenly told me that she was in love with her Dom. Apparently they also just talk about their day and they have sweet talk and cute messages and she tells him what she’s/ we’re going to do. She texts him goodnight also when she’s in bed with me even when I told her that felt really uncomfortable for me. She also said that if we ever became an actual relationship, he would remain in her life as a partner. That was a pretty big shock to me, especially because I had already started developing feelings and imagining what a relationship with her could look like.
Since then, the situation with him has caused a lot of tension between us. He sometimes calls or messages her while she’s with me, and at one point he was asking her for pictures of us together. He now wants her to share her location when she’s going out with me and she sends him selfies and when she’s not feeling good (threw up bc of alcohol) she tells him about it and not me even though I’m there asking hey are you okay you seem off. They’ve also been fighting quite a lot, and those fights have sometimes affected our dates and her mood.
More recently, they’ve talked things through and apparently taken a step back from their relationship. I can see that this has been weighing heavily on her too, and I genuinely care about how she feels.
But I’m struggling with what all of this means for us.
We made some agreements about how communication with him would work when we’re together, but those agreements haven’t always been followed. That has really damaged my trust. And now I’m at a point where I don’t just feel jealous or insecure. I don’t feel safe in the relationship. I don’t feel chosen. Our relationship during this dating phase hasn’t made any progress. There’s still the same arguments because she wasn’t honest in the beginning and I still don’t trust her because of it and it feels like in these past two months that really has been weighing on me.

I also don’t feel very validated or appreciated through words. Whenever I bring up that I’m struggling, she often responds by saying that I already knew about her boyfriend/Dom and that I knew she would be texting him, or that I need to trust her. She also says that he and I are equal and that I’m not her “priority partner.” I understand that intellectually, and I’m not asking her to pretend he doesn’t exist. But emotionally, it doesn’t feel equal to me right now. And when I try to explain that, she can become quite defensive, which unfortunately makes me even more insecure. I end up feeling like I’m asking for reassurance and instead getting told that my feelings are not valid our my own fault.
The thing I’m struggling with most is that I don’t know how to explain that “you should trust me” doesn’t actually solve the problem for me. Trust isn’t something I can just decide to have after agreements have been broken and I’ve repeatedly felt like there is another person sitting in the middle of our relationship.
I’m scared that I’m becoming more of a backup partner than someone she is genuinely building a future with. And I’m scared that even if she reassures me that this isn’t the case, I’ll never actually feel secure because there will always be this third person heavily involved in our relationship.

I don’t want to make her choose between us. I also don’t want to force her into a relationship structure that doesn’t fit her. But I do need to feel secure, valued and like there is an actual future for us.
So I guess my question is: how can I talk to her about this in a way that makes her understand that I’m not simply asking her to reassure me or “trust her,” but that I need her to take seriously what is making me feel unsafe?
And, perhaps more importantly, how do I figure out whether this is something we can actually work through, or whether we should just call it quits even though our goals and lifestyle and humour and energy levels do really match.