> Is it possible to have developed this without having trauma in my past?

My thought is that splitting or dissociation, of the kind that we usually talk about here, must be a psychological defense against some kind of trauma, something that overwhelmed the system's ability to cope with it in reality. Otherwise it would not happen. What that trauma was might be a question. Severe and prolonged abuse by trusted caretakers is certainly one possibility. Some almost "random" fear that arose in the course of an immature creature's life, for which there was not sufficient reassurance, could be another, it seems to me. Or some organically-based disease which was not well treated might start some such dissociation process. Maybe you can think of others.