I've had this same feeling and have tried to understand it. When I was younger and first had the feeling of me being me and not being everyone all at once, I had the image of a 'brain' floating in space pop into my head I guess as a way for my head to imagine what I was thinking about. Anytime I'm pondering something I always think about the 'lonely brain'. I took it as that was my realization that I wouldn't think like everyone else and that I would look at things differently always. Its almost like the realization that you've been given a chance at a unique perception oppose to that of the hivemind.