One step at a time...
I don't know how much tools your therapist has given you regarding relaxation techniques / changing thought patterns, I'm assuming here that he did give you some.
Try to find some small, reasonable goal. Easiest thing for you in level of anxiety. Then do it like everyday (applying said techniques), until you're comfortable with it. Your goal must not be to not feel any anxiety while doing it : it must be to stay until the anxiety has gone (always does). Victory is facing the anxiety, making the effort

– only way to learn that there's nothing dangerous there – so don't be too hard on yourself. Ideally you should even reward yourself for all kind of effort at facing the fear (no matter how small it would look to an outsider).
Good luck !
My mission is to kill time, and time's to kill me in its turn. How comfortable one is among murderers. (E. M. Cioran)