LJ - sore tailbone can be associated with sciatica or pelvic girdle pain, which is more common later in preg. Espec if it's worse when you're sitting. It's because all your weight presses down on it. Make sure you mention it to your ob, because if it gets to a certain point, then they may prefer to do a c-sec as you can break your tailbone in labour (nice, hey )

Re: diarrhoea, do you have any other lower back pain, cramping or tightenings? If so, I'd call the hosp / your midwife as occassionally these things can be a sign of pre-labour.

I'm not meaning to stress you out, so please don't panic, but it's better to be safe than sorry, so it will make you feel a lot better to make the call. They don't think anyone is being silly.

Take care

Jen