I used to suffer from depersonlisation/derealization where you feel you are not quite in touch with reality. It's a really strange sensation. You know who you are and you can think and feel everything around you, but you are not there. You feel like a ghost.
Christian Bale's character in American Psycho put it a better way:
"...though I can hide my cold gaze and you can shake my hand and feel my flesh gripping yours and maybe you can even sense our lifestyles are probably comparable: I am simply not there."
Don't feel alarmed!
Somewhere, something incredible is waiting to be known.