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
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