The anxiety does not 'cause' the symptoms. Your memory of symptoms does. This is more of a PTSD like flashback. You feel the concussion symptoms even though you have no physiological cause for them to manifest.

You need a better therapist who can teach you to redirect those responses to head touches and even thoughts of head touches.

It would be called desensitization therapy or exposure therapy or some such.

A good therapist will help you learn to believe these touches are not traumas.

A phobia therapist may help, fear of heights, claustrophobia, and other fears are similar to your fear of head touches.

This will all start with you believing these touches are not injuries even though you sense symptoms.

A protocol could start with you touching and even patting your head and focusing on relaxing as you do it. Then, you let somebody else touch then pat your head as you focus on remaining relaxed. Then, they touch or pat your head when you do not expect it and you focus on recognizing the touch or pat and returning to a relaxed state. This will need to be repeated many times, hundreds maybe.

I hope you can find a therapist who can help you. You might even mention this protocol. The therapist's goal is to help you learn to relax through each touch and pat.

btw, I bet that when you are distracted by other things, your tolerance for touches and pats is better. The distraction helps you ignore the contact.

My best to you.