I did not realise it was not normal to not recognise your own reflection.
It's not that i think it is someone else, its just that the face in the mirror does not mean anything to me. I am constantly mildly dissociated so this must be underlying it, as well as a lack of identity, and feeling like i don't exist. 

I also have this mildly with other people, even those close to me, when I cannot work them out, and they don't have fixed characters in my head, there is no continuity with how i see them, so their faces don't really 'mean' one thing to me, as they don't have a fixed identity in my eyes either. 

In fleeting periods when I have felt like i am my own person, and others are separate, distinct people, i have looked in the mirror and it felt so so different - i could see me, and it meant something to me, rather than just a round thing with eyes and a mouth and a nose.