Hi Sunflower.
I got this with baby #! too, but this time it's turned up quite early - usually when I sit or stand for a long time or overdo it - eg walking.
It's nothing to be worried about, just the joints in your pelvis are loosening up because of the hormone relaxin in your system. I used to find that my feet also hurt later in my pregnancy when I got out of bed in the morning - and I went up half a shoe size, which was not good since I was already a size 8!
*HUG* hope you feel better soon.
Sue