Jed - I have a broken Tail bone ( coxycc bone) and every time i get out of a chair it is getting worse and worse. I have been to the pyhsio and he gave me some stretches to do - but a tail bone is one bone that has no cure - even when broken all you can do is wait - mine has been broken for 3 years and since the extra weight of pregnancy it has gotten worse.
I find that sitting on a donut ring helps too - make you could go borrow one of the hospital - but you have to get up and walk atleast once an hour