So you are still concious and aware of whats going on around you when he is out correct? If you are and have always been co concious,with this other part then it is not a dissociative split. Dissociation Disorders are centered around a main symptom of time/memory loss/gaps. So if you are still always fully aware but trapped, then most likely not a dissociative alter. But only a trained professional can acureatly dx any condition. So i do suggest you talk to a pdoc or T about this. There are many reasons and conditions both physichal and psychological that could cause an extreme personality split. So without a professional pysch eval and posdibly medical tests as well to rule out any physical ailment that might be the cause...it is really impossible to narrow it down much. In the meantime if you need to talk about whats going on, this is a good place to find support and understanding Sorry this entity is causing you so much confusion and grief. please keep writing. We here can definately offer our experiences and what helps calm us when internal weirdness spills out into the world.