A few months into my pregnancy with twins (when they were tiny and didn't put any pressure on my back), I developed terrible nagging pain at the base of my spine. I asked all kinds of women about it and they said at the end of the pregnancy they had pain from carrying all that baby around. However, I wasn't doing that. I was a teacher and had been told by my doctor to do it largely from sitting. The last 2 months I was on bedrest, with limited sitting (on a couch or in bed). I delivered by c-section, so there was no delivery pressure there.
The pain went away, but now my babies are 22 months old and it's coming back worse and worse, for several weeks. I had no idea what was wrong, except my very tailbone hurt. (My husband thought it was quite funny I wanted him to massage it - but it's the only thing to bring relief.) I thought it was just my posture, which I'm sure contributes.
Now armed with information, I can seek help. Thank you again.