I have a bruised coccyx (very very base of my spine) - It has been a little bit sore for ages but I think I have aggravated it by doing sit ups on a hard floor. A few weeks later and it seems to be worse rather than better! I just googled and it seems that childbirth can inflame it so I bet I originally damaged it eight months ago when I had DD. It really hurts!
Honestly, it has been one thing after another since I had her: stitches that didn't heal for ages, inflamed cervix which caused bleeding, mysterious discharge, agonising rib flare . .. And I realise that my problems have been no where near as bad as the horrendous complications that some people have 
It has really brought home to me how much my body has been through and how bloody brutal childbirth is!