Hi Jo, I experienced pulling-type muscle pain in a line down the right of my belly button between 15 and 20 weeks. I think I was having a bit of a growth spurt. I too would recommend massage to the sore spot, only lightly though. The other thing is that when my digestive system was slowing down (I discovered I have to be really vigilant about eating heaps of fruit and veg every day) I'd get odd little pains here and there associated with that. HTH and enjoy the rest of your pregnancy!