Phz is right about PTSD. I was that way, especially when I was not dealing with the memories. I still repress and move into my head to take a break and distance myself from the pain. If I deal with it all the time I would break.
I was misdiagnoses for many years. I was diagnosed as Clinically Depressed and Genralized Anxiety Disorder...this is what they were treating. But the more the treated, the worse I got, like my body and subconcious was screaming that I was on the wrong track...not being heard. Then I had my first flashback. Before that people thought I was just a scatter brain...after my flashback I was tested adn diagnosed as PTSD. I learned that the anxiety is part of it and that some symptoms mimic BPD. I also learned that the unresolved issues are what was causing the depression.
But looking back I remember my mother laughing adn telling stories about me sleepwalking...she never took me to the Dr about it. Never asked why it started suddenly adn never did anythign but make homemmade alarms to wake her so she could turn me back toward my bed and walk me back to bed. I remember her telling me I would "fall asleep" standing up. I remember her always saying, "You wake up in a different world everyday!" All of this is dissociation....I was very young.
Don't know why I am rambling, sorry...lost my train of thought and spaced out...I hope you find the answers you need and some support here too...hugs.