One my sisters, who finally burnt the bridge some years ago, is like this. I ended the relationship with her for one reason. She refuses therapy, meds and all proffessional help.
Do you go to therapy? Cuz that's all I got.
BPD has a stigma, so it might be hard. BPD is a gift of childhood trauma, so I dont understand the stigma, but my therapist treats BPD without stigma when weve talked about it. The symptoms of BPD are treatable with talk therapy, and as you get older the disorder can be "outgrown" in age with talk therapy and 100% honesty with yourself.
Youve recognozied the patterns, how it is effecting your life, and identified the problem. This step, is one so many never make it to. Good on you for recognizing what is happening. That is a strong indication you can learn to cope, and navigate your way to skills for positive change.
If you do have a therapist, but arnt finding them helpful, start looking for a new one. It took me 6 therapist and two years to find one that I thought was a good match, and then another two years before I started recovering for my c-ptsd. A long road.
Life is a long road, so goddamn long, my 22 year old brain couldnt comprehend how fucking long life is. It can get better if you fight for yourself. You'll need a therapist, maybe join some group therapy, you can recover! Its worth trying!