As far back as I can remember; I have had a very prominent coccyx (tailbone). I could never lie on my back on a hard service or do sit ups. In the past few months it has become extremely worse. I can hardly sit at all. It feels like my tailbone is going to protrude through my skin. I don't know if there are calcifications or what; but there is very little tissue between my coccyx and my skin. I cannot sleep on my back any more; also my left leg tingles, feels numb at times and throbs painfully at times. Sitting on cushions does not help. It is becoming debilitating. I am 50, have always been very active; even ride a Harley. It's getting to where I can't even sit; but I can't stand for the rest of my life. Any ideas? Has anybody else ever heard of such!