As you probably know, this is a fairly common anxiety among TBI patients. As you appear to be suffering mightily, I doubt our reassurances will be sufficient to put you more at ease.

I would suggest that you get professional help, from a psychologist versed in PCS. Your local brain injury association might be a good sources of recommendations.

I think that I have yet to meet a TBI patient who didn't experience some level of anxiety and/or depression. It can be quite debilitating. Psychological assessment should be a standard part of the treatment protocol.

You aren't alone and your anxiety CAN be treated. Get the help you need.