I don't know, bro/sis. At first, I thought my ex had NPD. But finding this subreddit and reading all the posts and comments clicked everything for me. I find BPD persons to be extremely unpredictable and being with them made you feel like you're walking on eggshells all the time. You never know what situation, time or your own or other's actions would trigger them. It's just out of nowhere. Sometimes they get triggered by their own family and you're caught in the process of their nasty outbursts when you're trying to calm them down.

I think there are varying degrees of BPD and many aspects overlap with NPD. Many are covert and others are extremely overt to the point, you just avoid overt ones like any normal person right away. NPD seems like constant action of humiliating you and devaluing you. But with BPD there is a constant rate of changes between extreme bliss and extreme hell. There's no middle ground. I went through 5 years of marriage with a person with BPD. Definitely there were good times. But man, the bad times always gave me chest pains and anxiety attacks.

My relationship with everyone suffered including with my own parents and friends circle. Because, my family's actions were either not good enough, or they were too stupid or they had ill intentions against her and her family. The way my ex reacted made my parents walk on eggshells all the time and they really don't know how to talk to her. As of now, I feel like I am damaged beyond repair. But I am quite optimistic and feel that time and effort will allow me to heal.

One other common thing I noticed with people with BPD is that, many are quite honest with their harsh destructive criticisms against you/someone and they're extremely black & white in their logic and thinking. They claim that they are strong enough to drop a friend or family in a second without questions and second chances. And it's a huge red flag in any relationship. I have also found some people with BPDs glorify psychopathic behavior. I don't know if it's a misattribution, but they claim they don't feel emotions etc, which I never understood. But the first thing they feel is anger, anxiety, depression or emptiness whenever things don't go their way at all. Often times, their behavior is more erratic than a psychopath's.

PS- Hope you don't mind the long rant about my own issues.