I have a strange feeling of claustrophobia in my own body. what is this caused by?

Anxiety: Give your therapist a call and have her consider changing, increasing or adding on to your antidepressant medication. Also ask if there are sessions available to teach coping skills, meditation, and less self absorption. Those really help and last a life time.

You: Are not the only one. There are millions and nobody knows for sure. It may be useful to visit a board certified psychiatrist.