Update. I have read about a nerve condition, "pudendal neuralgia", which can be one sided, and my tenderness was a bit one sided, but mine doesn't feel like I would think nerve pain feels (i.e., electric, wired). Instead, my pain feels like tenderness in broad area of the coccyx, and not just a "point of pain". Also from the book "Tailbone Pain Relief Now!" by Dr Patrick Foye is mentioned dynamic instability of the tailbone verterbra, but I'm usually generally described as rigid and tight, not loose. My personal training progam is focused on improved movement, as a result of my result of my score on the Functional Movement Screen. It also doesn't feel like arthritic pain, another type of tailpone pain the Dr Foye. In sum, it feels like bone ache from soreness and tenderness, and I can't see a clear fit to the conditions mentioned in Dr Foye's book. But then again, I may be overfocused on the pain spot, and the pain may be caused by problems elsewhere (e.g., nerves). In sum, the thing that stands out is that this is chronic for almost a year now, and is not healed by a general fitness program and general good health.