I was rereading your post and noticed something. in it you state...

I don't know why I've encased their body, and have been sent to witness them on the planet earth, as A creature from another , universe, plane of existence, realm, etc. . The body I live with has become familiar, but I still know it's not mine.

Dissociative disorders in my locations do not include believing one is an alien from another planet possessing a human body to watch learn or witness them.

here in my location this happening is called psychosis (which having psychotic symptoms are a part of having bipolar disorder)

with DID the term possession it is a cultural description not a situation where aliens come to earth and enter a human beings body.

some cultures (for example native american) use the term possession instead of words like feeling numb, feeling spaced out, feeling disconnected, dissociating, sense of agency, and ownership

my suggestion contact your treatment providers, they can adjust your bipolar medications to help with this problem.