Losing myself

[B1125]

(Background: my fiancé has bpd) So, about a week ago I was handing my fiancé her phone when I saw her ex, who's one of my fiancé's roommates, had messaged her something about being in an open relationship with us. I asked my fiancé about it immediately and soon enough she told me about how they had recently been alone together, cuddled and fallen asleep in the same bed...she told me right away that she wasn't interested in an open relationship and only wanted me.
I acted with my brain instead of my emotions. I just wanted to walk out but I stayed and asked questions like when that had happened, if she planned on telling me, and so on, to try and understand. What gets me the most was that after she cheated, she was still seeing me and would be extremely defensive when I'd point out weird things I had noticed between her and her ex. We had some of my favorite memories while she was being dishonest with me. I can't look back at any of it now without the sour feeling. I decided to stay with her though, I genuinely love her so much and don't wanna imagine us splitting up. But I'm beyond hurt, and no one to talk to about it. She told me to tell her what im feeling, thinking about. I told her I dont think she's ready to hear how much she's hurt me, considering how self deprecating she can be. Anyway, she made me feel like I could share my feelings but when I did, she *trigger warning* cut herself and made suicidal comments, because of how guilty she felt for her actions. We stayed up for hours, me just convincing her that I dont hate her and that I still want to be with her. Eventually she just got too sleepy to keep talking so we went to bed.
I haven't stopped thinking about what happened, I still feel like a lot is unresolved, but we dont talk about it. Im terrified to bring it up, but I have issues with trust and commitment on my own. So while im tending to her needs, mine are not being met. I can't be there for her if im not all good on my own. But she's too insecure to let anyone else into my life for me to have other support systems. Im at a loss. I dont know what to do. Im still loving and there for her every single day, but I stay up all night without her knowing, just crying, journaling, trying so hard to heal but I can't heal alone. She doesn't even know Im making a post like this. I dont want to lose her. But im about to go on a five day family trip and her ex still lives with her. Im absolutely horrified, my trust in her isn't completely back yet. But I dont even know how to begin the conversation without it turning into me having to talk her down. I know she feels bad for what she did. But Im not confident that it won't happen again. I think she's scared of me leaving her, of me hurting her, so as a coping mechanism she tries to self-sabotage. Ive pointed that out and she agreed, I've been doing my best to reassure to her that I won't leave her. But I've just lost so much self esteem that its hard to be loving and reassuring when I need that same treatment in return. She promised to be better to me, but that lasted for a short amount of time. It was difficult to be intimate with her again but I forced myself so that she wouldn't feel like I dont love her anymore. me hiding so many of my feelings is hurting our relationship. but I dont know where to begin on fixing it. yes talking would be ideal but I cant be real with how I feel to her, she takes it on too heavily

[RELATIONSHIP PROBLEM SOLVING]

RELATIONSHIP PROBLEM SOLVING This is a high level discussion board for solving ongoing, day-to-day relationship conflicts. Members are welcomed to express frustration but must seek constructive solutions to problems. This is not a place for relationship "stay" or "leave" discussions. Please read the specific guidelines for this group.

[Cat Familiar]

So you’re trying to be supportive of her, while this isn’t reciprocal. You’re not able to communicate how you felt about her behavior with her ex, without her threatening self harm. And then, you had to reassure her you love her.

Yes, it’s unresolved and if you don’t make changes in what you’re doing, the same patterns will continue over and over—lack of emotional support for you, and you stuffing your emotions and trying to reassure her.

That she is isolating you by being threatened if you seek emotional support outside the relationship is abusive. It would be even more obvious to you how abusive this is if the genders were reversed. You deserve to have a good support system in your life, especially with a BPD partner. Now is a good time to find a therapist that you like. After all, even therapists seek therapy when they have a difficult BPD client.