I feel like I have a touch of this sometimes and it really does get worse the more I let it get out of control. I don't have a regular job so I don't often have to leave the house except to run errands or see friends. If I don't schedule that kind of activity regularly, I tend to start dreading it. I don't really understand why. It just seems to be too hard to step outside or to interact with people.
Of course, when I actually do go outside I enjoy myself and feel fine afterwards. I think it's just a matter of getting used to the world being one way or another.
And I only feel a very mild anxiety. I have the deepest sympathy for anyone who has full blown agoraphobia. It must be very difficult to overcome.