I would like to mention that each case is not the same, brain injury can be highly unpredictible and highly indiviudualized and even though trouper is able to write clearly does not mean mild Broca's is out of the question. Regardless, it is more than just anxiety, it sounds neurological to me.
Supertrouper....keep a pillow with you so you can bang your head on that to prevent further damage. You could end up knocking yourself into a coma, so try to find something soft before banging if really cant prevent doing that. I know what it is like to do self injurous behavior. I used to bang my head on the floor as a kid, and then quit that when I was 7 or 8 and went on to biting, scratching myself after that. I understand that sometimes it seems like it is beyond your control to stop, but try to delay it till you find something softer to hit your head on. Brain injury is serious buisness and do whatever you can to prevent further damage. The good news is the brain does heal...they used to think that it doesnt, but studies show that it does, but very slowly. So if you can prevent further damage, you will get better over time. Also you need to see a speech specialist.
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All art is a kind of confession, more or less oblique. All artists, if they are to survive, are forced, at last, to tell the whole story; to vomit the anguish up.
-James Baldwin