confusedondid I can relate to your memory problems a lot. I was diagnosed with DID a few months ago and I also struggle with knowing if it is real or not. Sometimes certain experiences like being aware of others make me feel like yeah, this is totally real but then other times it all feels like an awful lie to me. I am still coming to grips with it and trying to understand it.
I have had many experiences like you when people talk about things that I suppose I should remember but have not even the slightest recollection, other people have shown me photographs too of "me" at this party or that party dressed up in costume or whatever but I don't remember the slightest detail of that supposed event. Well I suppose it must have happened because there is a photo of "me" there. Sometimes i think I "should" remember stuff like that but I don't. There are photos of me with people but i have no idea who they are and other people talk as if I should know them but I don't. So all I can do is assume that must have something to do with DID but it really all feels so surreal it is hard to be sure.
ANyway I just wanted to let you know i can relate to that part of your post.