Years ago I posted my sufferings to this site just like you. My world was ending as I knew it because I could no longer tolerate riding my Harley.
I didn't know what was worse, the sharp stabbing pain while riding or the mind bending lightening strike that went from my tailbone, up my spine to my brain when dismounting.
Long story short... I found a Chinese Acupuncturist who was also a Chiropractor. He put what felt like 4-6 needles along both sides of my Coccyx, some deeper than others, and attached a rotating point stimulation device to them.
He turned the settings up one at a time to where the muscle contractions just started to hurt, then backed off. He said the pain was from weakened or torn muscle attachments that never or didn't heal properly from a fall. Or that something like sitting in a poorly constructed chair for over time at work or school was the cause. And, how this treatment would build back the muscles as if they were pumping iron.
It took three one hour treatments a month for three months, but my Coccyx pain has NEVER RETURNED! It has been YEARS now, and the pain is a distant bad memory. I happened to drive by his office the other day and there is a dentist there now, so please don't write asking for his info. Seeing the place made me think to write and share my cure, with the hope this info might help someone else.