For those saying OPs boyfriend has no right to know about her diagnosis, there's another side to this situation.
I watched one of my brothers in a relationship with someone with BPD. It was really difficult to grasp just how 'in' to him she was very, very quickly. That's not to say my brother isn't lovely/lovable, he very much is. Rather, it was the rapidity of him being, in her mind, basically the best man to have ever walked the earth.
The control/need for his constant presence/attention came first. The control of his whereabouts, even visiting our parents became a reason to believe he had abandoned her in favour of others. If he wasn't home by a particular time, she'd start calling my parents literally one minute after he was 'due' home, out of control sobbing and screaming that he didn't care for her.
We watched on as that idealisation turned, seemingly overnight, to devaluation of our beloved brother. She'd tell anyone who'd listen he was mean, selfish, bullying, heartless etc. etc. None of this squared with the man we know.
Then the threats of suicide began if he didn't do this, or if he did do that.
Because he is so nice, he became her emotional prisoner and punchbag, scared he would be the cause of her killing herself or, at best, harming herself. For context, our other brothers would not have tolerated her behaviour, and would have walked away a damned sight sooner.
When he did eventually gather the courage to leave the relationship, with a lot of support from our parents, our other brothers and me, the violence and threats were added to the suicide threats.
As he was gathering his belongings she started assaulting him, hitting him with anything she could lay her hands on and screaming she would tell everyone he'd raped her.
The brother, with whom my brother was staying until he got himself organised, had his wife's car vandalised with 'SLUT' 'CUNT' etc. sprayed all over it.
The police told us she'd intended damaging my brother's car, for 'abandoning' her, and because it wasn't there she just damaged my SILs car instead to 'relieve' her trauma at my brother having 'abandoned' her.
So, yeah, this man deserves to know the history of the OPs behaviour towards her exes.