I've felt like that (especially from 14-35) and periodically on and off. I feel like I'm not there (or that my personality has gone on a permanent hiatus) and everything just goes thru me and doesn't register with me. No matter how hard I try I don't have control over it. I can not figure out adults who are in-touch with themselves 24/7. (I have not felt like that since 13 or so and really frustrates me.)