To answer your last question:

You have all these diagnosis because you have been in the mental health system for 18-20 years (?), jumping from therapist to therapist. But instead of doing the work required to utilize therapy to improve your real life, you have spent years struggling with therapists trying to get what you want from them. When the therapist failed, you moved to another therapist.

Instead of using the therapy as a vehicle to change your real-life relationships, you have spent years focusing on getting a therapist (a job) to fulfill your perceived needs. You have not focused on yourself, but focused on you and your T.

Most people want to use therapy to improve their relationships with friends and family and self. Until you give up your fantasy that your T is more than a "job," you will continue to stay in the system. They will continue to make money off you. IT is there job and they are happy to do it.

Beside BPD does not necessarily have anything to do with a poor childhood.

It has to do with how the infant perceives the relationship with the caregiver. If baby cries and mother is too tired to respond, baby could perceive that as abandonment...... No abuse or neglect. The baby's perception of abandonment. The literature is clear on this now.
There are even cases of BPD adults who had colic as babies. Because the caretaker could not soothe them enough, the baby perceived it as "caretaker is not helping me, caretaker is leaving me in pain, caretaker has abandoned me." When in actuality, caretaker might have been holding baby the entire time.... colic is just hard to soothe away...

Your label is because BPD are known to move and quit therapy and be long-term clients.

Most people your age would be looking towards spending as much time and energy with those that love them (grandkids, kids, etc). In the end, those will be the people that remember you and think of you frequently. Your T will fill your spot with someone else and be glad to take their check.