So who hasn't dealt with this with you pwBPD?
It can drive you crazy. My pwBPD has been accusing me of affairs for a while. At first I thought it was kinda cute. Like I was flattered that he thought all these guys liked me (I know I got issues

) But it swiftly turned sour and really began to hurt my feelings that he would think I would do such terrible things to him. Of course I would try my hardest to reassure him that I love only him. But he had concocted all this evidence that was "undeniable proof" that I was sleeping around with people right under his nose. (This proof was him planting recording devices in my purse or around my house and listening to them saying he could hear me with someone his paranoia was getting outta hand)
So for months my anxiety was mounting. I was so drained and depressed. And always trying to show him my loyalty, isolated myself from all male friends... Deleted any old male friends numbers and contacts, even got a new number, got off fb... etc. Basically was losing a sense of myself.
So you probably have been and are in this current situation. So what do you do?
What has worked best for me is I had to first start taking care of me. That included really getting my anxiety depression and health together. No more weed alcohol and unhealthy foods... more exercise. And prayer I had to go to God about all this. I also began to inform myself about BPD. Im a resesrch information junky anyway so it kinda became an obsession. With better mental emotional and spirtual clarity. The light bulb finally went off. I realized that i never had validated his initital feelings ever. In fact I realized that all I ever did was consistently invalidate his experience. I began to see that my pwBPD was soo insecure and struggling so much with feelings of worthlessness. He's really really good looking so it just never occurred to me that he felt inadequate and had really really low self esteem.
I realized one day that despite how insanely abusive controlling and paranoid my pwBPD was acting... .He actually was really really afraid and feeling depressed and unworthy of love. He really thinks that I will just throw him a way and find someone else whose better looking and more desirable and better in bed. And the pain is unbearable. He always would talk about a gnawing feeling in his gut my response oh that's probably indigestion or your just being paranoid. When I think back about it all I made alot of mistakes and was really insensitive and uncaring. It's hard to admit that cause he was such an a#$hole and cranky and controlling.
So basically I had to learn empathy validation and listening. I sat down one day and let him tell me again all his complaints. It was soo hard to hear because they are about me. But I just listened and then I repeated everything back to him. Then I really began to see how if I had BPD I might have come to those same conclusions. I took his hand and said wow it must really really hurt to think that someone could betray you that way. I'm so sorry I never took the time to listen to you. This has really been torturing you from some time.
He was like YES! You finally get it!
I thanked him for being so brave to share with me his feelings... .that's hard for anyone to do.
So this was the first of many conversations we had. He didn't just initial stop being jealous. And he's still trying to work it out and still comes to me about the same issues. But we talk about it and I just listen empathize and validate.
Your pwBPD needs loads and loads of this. BPD is a debilitating scary mental illness. It's stigmatized and our loved ones suffer so much. It's really challenging to do all this compassion when they get emotional. But learning these skills and taking care of yourself first will help you to get your life back. You are the only one who can change.
It really works!
Peace