I have had similar experiences. In times of extreme difficulty my mind can split and different personality types will live alongside me and sometimes interact with the world. However, they are not full fledged personalities and I do not have DID. They usually disappear for the most part after I have processed the event, and I still retain primary control throughout.

I also live in an almost constant state, of varying degrees, of depersonalization and derealization. I often fade out and come back to myself without any real control over it. I tend to have to check my body to see if I've performed basic hygiene recently (like showering or teeth brushing) because I can not remember. I have an absolutely horrible memory. Taking in and retaining information is extremely difficult. I have also experienced something akin to fugue states where I lost all memory and had no clue who I was. I probably would have traveled if these states had lasted more than a day and nobody had been with me at the time.

These are all forms of dissociation, but most do not meet the criteria for a specific dissociative disorder. When it is severe, as in my case, they may diagnose with dissociative disorder not otherwise specified (DDNOS). However, dissociation is also associated with stress not related to mental health disorders, and with completely different mental health problems. I could not tell you much else without more information.