Thom, 99.9% you're right... it's you sitting at the computer hour after hour... I've had the initial symptoms of carpel tunnel and sore shoulder for years... and a chiropractor of one sort of another has kept me from surgery. (I'm 67 and have been at a keyboard for since I was 20 or so.)
Look for one who does muscle testing and knows chiropractic isn't the answer to love, life and the universe and everything... I go once a week to a real healer and stay out of allopathic medicine for things like this...
Walking is wonderful... and get set up ergonomically for the next books... and force yourself to take 10 mn stretching breaks every hour and a half or so.
Keep us posted - we need you writing.