there are different types of dissociative disorders. borderline personality disorder has the type where if you get overwhelmed or stressed out, you can experience dissociation where it makes either your surroundings feel unreal or like you are in a dream or where it feels like your thoughts and feelings don't feel real or belong to someone else or you lose your sense of identity. it can also cause you to forget events due to the dissociation because of how affects the brain and shuts it down/disconnects from self/surroundings.

dissociative disorders can also exist separate from borderline personality disorder which could be any type including DID and similar ones with alters or not.

i have a diagnosis of borderline personality disorder (though not the classic type) and am moving away from the diagnosis. but i also have DID as well as OCD...but within all of those disorders, i also experience a lot of trauma symptoms, so for me, most of it is trauma based.