Try to reduce your anxiety as much as possible. I know that this is easier said than done, but you may want to see a psychiatrist about your anxiety. What I am saying is that sometimes thinking about a medical issue can cause you to notice it more and the stress can actually cause a response. I am not a doctor, but from my experiences with PCS (4 months in) I have had muscle twitches, hand tremors, pulsating head and neck, with a noticeable pulse in my neck since the injury. I think that PCS can present in hundreds of ways, which makes it such a mystery. These muscle issues seem to be rare but still normal for some people affected by PCS. Remember that you have been tested by a number of medical professionals and try to have faith that they would have caught it if it was something more serious. Just my two cents, man. Take it for what you will.

I wish you well in your recovery.

Best,
Danny