Hi Dee,
I haven't had pregnancy-related tailbone problems, but my hip clicked all the time towards the end of my pregnancy, and it hurt too. I just assumed it was normal at the time, but now it still isn't quite right. I keep forgetting to ask my doc about it... Perhaps if its bugging you it'd be a good idea to mention it to your HP at your next visit? Can't hurt to ask anyway.
All the best for the rest of your pregnancy - not long to go now!