What you are experiencing is called Depersonalization/De-realization.
I suffer from panic disorder and know a lot about this because I experience it as well.. These symptoms are COMPLETLY normal and are in fact just another symptom of your anxiety disorder, although they are very disturbing feelings at times, I can assure you that they are completely harmless.
Depersonalization can be anywhere from a change in a persons self awareness, feeling like you are detached from your own body, feeling weird, unfamiliar to your surroundings, and ever two dimensional at times..
De-realization is when you feel spaciness, foggy head, withdrawn from yourself, distant from your surroundings, or dreamlike...
Okay so now you ask why does this happen?
Well It was explained to me that They are actually caused by changes which occur in the way nerve signals are processed by the brain during anxiety disorders, but keep in mind both are directly caused by and are symptoms of anxiety, they are as I mentioned before completely harmless!!
I know these feelings can be very disturbing at times, but when you feel this way just try to remind yourself that it is all part of the disorder and you are not suffering in anyway from mental illness!!! It's all a just a vicious cycle and your brain is only reacting the way it should..
Are you getting any treatment for your anxiety/panic disorder??
I hope my explanation was able to help you some.. Any thoughts or questions feel free to ask. If you get a chance look up my post my disease called anxiety disorder on this board, I think you will find some interesting information and explanation's on anxiety and panic disorders as well as that you are not alone in what you are experiencing... feel better boxerlover