I'm pretty sure it was around 12 weeks that I started feeling cramps associated with a stretching uterus. They weren't intense pains, but similar to strong period type cramps. Hopefully that's all it is for you.

Oh, and I sympathise about telling little ones to stop jumping on your belly. My 2 1/2 year old DS seems to always get a well timed kick to the belly during nappy changes, and likes to climb and lay across my lap if I sit on the couch. Rest assured that there's lots of padding in there for the little bub