Each of us exists in our own world. "Reality" is a word that means little - it is created of a combination of each individual person's perception of the world. This perception creates an individual existence.
But each person's world also includes the people they know, live with, and come across as their life continues. Therefore there must be many, at least ever-so-slightly different versions of us. One version for the world of each person who knows us. Each version will differ because of each person's different perceptions of us, although the versions of those who know us best will overlap. And all those many versions of ourselves branch from the existing original around which our own world rotates. And all will be us, just slightly distorted.
This means that you are living many different existences, all at the same time.