Do you ever feel like you're literally "not yourself"?

Increasingly often these days I feel confused as to who I am. It feels strange that I am who I am. Sometimes my name sounds unfamiliar, and my family members seem like strangers. Very strange. I'm 20, and am very close to all my family members. I have little memory about my past (I have very bad long term memory yet above average memorizing skill) and everything in my past feels like my previous life of something. Like nothing ever happened, and I am nobody. Sometimes I think maybe I'm just an impostor. And I ask myself, do I really exist? Is everything just an illusion? I have a long history of depression and social anxiety. Do most people have these feelings too, or is it related to some disorder? Thank you.