Hello Knitting: Thank you for bringing your concern here to PC. I see this is your first post. So... welcome to Psych Central.

We here on PC cannot suggest mental health diagnoses. However perhaps other PC members, who have been diagnosed as having BPD, will recognize some of their own experiences in what you wrote & will want to share them. You titled your post: "Possible Quiet BPD". Family therapist, Kati Morton, has a video on her You Tube channel on the subject of the quiet borderline. Here's a link just in case you're not familiar with it:

YouTube

And then here are links to 3 articles, from Psych Central's archives, on the subject of BPD:

Borderline Personality Disorder: Symptoms & Treatments

Living with Borderline Personality Disorder

6 Gifts of Borderline Personality Disorder

I hope you find PC to be of benefit.