How far down does your spine go ? and then what ? I sure am having some funny pains. sharp cramp last for a sec. then gone.
Sounds like you are having small spasms. Tail bone doesn't usually have problems unless you land on it and break it or something.
Hips and pelvis is a web of muscles and nerves. Very easy for something to get tweaked. 2nd picture doesn't even show them all. It's amazing it all works!

