Preface: I have BPD traits as well as bipolar 2.
I've recently been to an extended outpatient program at a psych ward where I was reassessed in terms of diagnosis and re-medicated. I am now on a combination of antidepressants and mood stabilizers in a slow release instant release mix (don't feel comfortable sharing what medications online) and my symptoms have improved substantially.
Before this outpatient program I was having extreme lows with suicidal thoughts very frequently, now I have them a lot less frequent but when they happen their intensity isn't any less horrifying than it used to be.

Aside from medication I've also been working extensively with DBT for a long time.
I am polyamorous and in 2 long term relationships that have been going on for 4 years and 12 years respectively, my partners are very affirming of my issues but themselves sometimes struggle with communication and staying in touch (long distance).

Most often what happens is that a series of tiny miscommunications, misunderstandings and (honestly) unfounded feelings of rejection will build up until I end up in a state of mind where I feel so self hating that I am trying to convince everyone I love to ditch me because I'm "that horrible".
In those states I feel suicidal because it feels like everything is hopeless and all my relationships are ruined.

Things are better now than they have been but gods-damn, they are unbearable when I'm having one of those episodes and I am absolutely terrified that one day the people I love will have had enough and they will leave.

I guess my naive and pathetic question is if any of y'all with a similar experience (ignoring the polyamory part, I know thats not super common especially with BPD) have found anything that helps.

I tend to just try and regulate my emotions with DBT and restrain myself from saying some dumb shit to my partners but it feels like I'm fighting a losing battle and like its only a question of time till everyone will hate me as much as I do in my worst moments.