Hope, there's a guy you can find on YouTube that you might like (or might not!) named Dr. Colin Ross, who runs some inpatient programs for people who've suffered severe trauma. What he has found is that no matter what diagnosis a person is given, if you help them address and work through trauma, their symptoms will improve. It doesn't matter if it's DID, psychosis, schizophrenia (which often has links to childhood trauma as well as to biology), BPD, or anything else -- if you treat the trauma, the person's life improves. I think this is a good way to look at things. T's can put whatever labels they want on things as long as they are willing to work on trauma with you, because that will help.

I also wanted to say that in some ways BPD looks to me (as a complete layperson -- my opinion is what you paid for it) like an attachment disorder, and it reminds me of things I've read about disorganized attachment. A person with disorganized attachment basically doesn't know how to insure an attachment with another person because when they were a little kid, they tried everything and nothing worked. So sometimes maybe they faun over / idolize someone, sometimes they flee them, sometimes they fight with them, sometimes they freeze (shut down) -- but those are actually trauma reactions and none of them really work for attachment, but that is not the person's fault. If they had been allowed secure attachment as a child then they would know how to do that, but they weren't. Lack of attachment as a young child is a kind of trauma and it makes sense to still be having trauma sorts of reactions when attachment is threatened. I think there are many ways to look at these things and we should try not to get locked into any one label or model for things.

You are a person with your own unique history Hope, and your T can't define your story just by putting some label on a few selected traits. The label may be useful to him in doing his professional work (like writing prescriptions) but it might be irrelevant to you. Figuring out what you do want to work on, like some of those borderline traits you do see, or attachment issues, or trauma -- that is what you get to define. Stick with him a little while longer and find out if he'll do this with you -- if he will come on your path with you.