i didn't know growing up but knew when i was in my early teens after reading things/talking with others online who had similar experiences with and without a diagnosis of it. i didn't think i had DID just because of not blacking out between switches, but i heard voices in my head and knew some of the others and had them talk to me and share their names. i was able to piece together things about each of them over many years. i experience them as other parts of me, their own person, which is different from me.

i knew it wasn't 'normal' because my functioning was different than most people i knew, and i knew that most people didn't experience separate people like that in their head or randomly blurt things out they weren't thinking, didn't have have a messed up sense of time and forgot things, didn't have inconsistent and contradicting ways of thinking/feeling, etc. that didn't match up with situations, and had more of a sense of who they were.

i just knew even before seeing a professional and being diagnosed.