First, I haven't been diagnosed with BPD but relate to everything
@KwanYingirl describes (I've suspected at times that I'm somewhere on bpd spectrum, though relate much better to the "unofficial" list of cptsd symptoms). I get along very well with others but avoid intimacy also. I feel like I have a wall around myself often and I find it hard to move in therapy, too, and that I only warm up to people to a point. I have weird, very childish self-other problems at times, like people just stop existing (like really young object constancy stuff) or I do...some conglomeration of trauma and attachment problems, no doubt.
All that being said, I had a load of difficult symptoms when younger. I don't know why or how I wasn't diagnosed with BPD, but specialists were so busy playing whack-a-mole with my dangerous symptoms (eating disorder treatment here, alcohol treatment there). BUT I did improve, pull out of the constant self-destruction and I do have more positive connections. I'm not dealing well with some new body stuff, but it's just another layer I suppose. I manage to reach out vs entirely collapse upon myself.
A friend of mine goes to DBT group and finds it very helpful. I personally like the "group therapy" sort of thing because I feel safer and not like I'll be exposed as having problems...because we all do...so it's much easier to communicate. My thing is 12-step meetings, and the group of people with shared experience has really helped me "be myself" more around others and develop some amount of trust in other humans.
From my understanding, whether BPD, PTSD, or CPTSD, minimizing of symptoms and recovery is possible...and relationships are possible too. None of this comes as fast as I want it though. And it takes work and support and sticking with it. Do you have a therapist you are working with?