Tail bone pain no injury?

See below. Sounds like you have coccydynia or 'tailbone pain'. This can occur with trauma to the tail bone, abnormally positioned coccyx, or poor sitting posture. Try using a good lumbar support to help shift your pelvis forward. This will put the pressure on your ischium. (bottom part of pelvic bone), and will shift the weight off of your coccyx (tailbone).
Coccydynia . Coccydynia refers to pain in the region of the coccyx. Most cases are associated with abnormal mobility of the coccyx which may trigger a chronic inflammatory process leading to degeneration of this structure. Nonsurgical management remains the gold standard treatment for coccydynia, consisting of decreased sitting, seat cushioning, coccygeal massage, stretching, local injection of steroids.
Coccyxdonia. Painful condition, takes a while to resolve. See your doctor for x-rays/mri to make sure it's nothing serious.