The last thing that got me was that he said my husband and I have to keep working hard to gain back his trust because in my mind I'm like "Are you kidding?". We go through these ups and downs where we're the best parents or we messed up his life.
I think that resolving to take care of yourself first, ensuring you're in a calm place, is spot on. The key is not to take your son's words personally, hard though that might be, and despite how hard your son tries to convince you that you're awful and you're the reason his life is a mess.
I highlighted your comment above to point out what I think your son is doing, which is projection and blame-shifting. In my opinion, that happens when he's ruminating endlessly about his perceived faults--in this case, breaking trust, lying, etc.--which induce in him a deep shame. He's so plagued by these negative thoughts that they emerge as projections onto other people. To me, that's a hint about what is really bugging your son, especially if this is a recurring theme of his. He's ashamed that he's lied or otherwise broken your trust, possibly about his drug use. Maybe he feels his entire life is "fake," like he has impostor syndrome, that he's just "pretending" to function like an adult, when inside, he's still feels like a little boy. Maybe he feels that if you really knew what he was up to, he'd embarrass you. Underlying all this are probably feelings of shame, inferiority, disappointing you. He's so worried about it that his concerns emerge as projections and accusations.
Why does he do this, you might ask? Because with BPD, overwhelming emotions are hijacking his rational thinking. In addition, it's very common for a pwBPD to play the victim and blame-shift, even if he has to distort the truth to do it (which is why he sometimes might appear "delusional"). To him, his feelings of shame are unbearable. To him, a standard coping mechanism is avoidance (e.g. procrastination, numbing feelings with drugs), rather than dealing with problems rationally and progressively, a little bit at a time. Instead of taking things in stride, putting things in context and having some patience and perspective, his thinking is black-and-white, catastrophic, and intensly personal. Instead of tolerating distress or discomfort, he's impulsive, often self-sabotaging. Think of it as a fight-or-flight, trauma-based reaction in ordinary situations. And instead of working towards long-term goals, your son is stuck in the past, rehashing ancient grievances, to avoid dealing with today's problems. Instead of taking responsibility for his life, he's blaming others, mainly YOU. On these boards, I've written countless times how I think that the victim mindset is the worst part of BPD, because it renders him powerless over his own life, as he expects everyone else to change, not him. Sound familiar? If it does, it's because that's BPD, and I've seen it all, many, many times with the pwBPD in my life.
But getting back to my original reply, I think it's fantastic that your son is getting therapy, and that he has a diagnosis, and that he's still talking to you. It must mean that he's come to the realization that his standard tactics of using pot, lashing out and blaming you aren't really working for him anymore. Look, pwBPD often dislike the diagnosis, as there's a stigma, and the words "personality disorder" seem pejorative. But in my way of thinking, he just needs a extra support right now to learn better emotional coping skills. Instead of framing it like a "disorder," frame it like getting support to overcome a rough patch in life. Instead of beating himself up about personal defects, frame it like getting some life coaching, or maybe "executive" coaching, or maybe cognitive training. My understanding is that the skills emphasized in DBT (the gold standard for treating BPD) are mindfulness, managing intense emotions, reducing impulsive behaviors, improving problem-solving skills and improving relationships. Those are skills helpful to just about everyone, and they're not necessarily taught in the home, let alone school. I don't see any shame in getting professional support and training. From a guy's perspective, he could think of it like brain training--increasing mental toughness. That's no different than building physical toughness at the gym!
Anyway, if he's in a good mood, you might comment how proud you are of him taking care of his physical and emotional well-being. That's what responsible adults do, right? I think that if he tries to blame you (Well, it's your fault I need therapy because of my terrible upbringing), I'd advise, don't apologize or fight him on that. I think you stay in the present (I love you and I'm proud of you for taking care of yourself.)
Just my two cents. All the best to you.


