29 weeks and sore belly.

I am 29+3 weeks. I seriously am all belly and for a few weeks now I have been having a sore feeling across my stomach. Baby boy is constantly moving all around my belly button and above pushing out. With my first son, he was all over my belly and the placenta was in the front.  This time the placenta is in the back and I'm thinking that's why I'm experiencing this soreness. Anyone else have a sore belly?