You should mention this to your therapist. This is not uncommon at all and in fact has a name. Derealization and depersonalization are the terms used for this. They are common to anxiety. Here is a LONG journal that talks a lot about this. But you need to talk to your care provider/therapist as well so that they understand what is going on with you and can best help you.
Here is the journal:
http://www.medhelp.org/user_journals/show/11569/Derealization-and-Depersonalization-VERY-common-anxiety-effectsplease-read
good luck
Dear, this is a very common anxiety symptom - So firstly what you need to do is worry less. - calm down and practice good things like exercise, going out with friends, etc... don't worry about the derealization etc - they will go off on their own once the underlying reason for your anxiety is solved - which i think in your case is GAD/Panic attacks. Please do tell this out to your therapist and you'll be just fine soon... God Bless