I'm not sure if it will help, because I am somewhat older than you. But I have both borderline traits and a dissociative disorder, as well as PTSD. Which is why I find complex PTSD so much more explicit. If I could have my own name for it I would call it Relational Trauma Disorder, because trauma mainly through relationships/neglect/abuse has caused my symptoms.
Remember severe dissociation is one of the BPD traits. The thing is that in the criteria its 'transient', same for paranoia. When its more than transient, it becomes getting towards a dissociative disorder instead of or in addition. I don't know where they draw the line though!
There's DD NOS [Dissociative Disorder Not Otherwise Specified, which is not quite as intense as DID.]
This article
Understanding dissociative disorders [link] by Mind might be helpful.
I can't diagnose you, nor can others here. But I can very much relate to a lot of what you describe, however its labelled or not.
My therapist and I talk a lot about me, and the Other One as we call it, who is a split off dissociated self who takes over now and again/a lot of the time, and takes me back to being in the past, although it's now... More here -
dissociative distress thread *Triggering (Abuse)*