Do you think it could be dissociation ?

http://www.myshrink.com/counseling-theory.php?t_id=13

I dissociate a lot because of anxiety and trauma...I can definitely relate to feeling 'not here'. Maybe not so much the other worldly stuff but what you're describing makes sense to me.

I sort of 'leave' reality for awhile. Apparently it's quite a sophisticated coping mechanism, and treatable.