15 weeks pregnant. When I roll over sometimes, I get a pain in my side. When I get up sometimes, the pain.....

The pain is on both sides and it is like a stabbing pain. It happens when I roll over too quick or sometimes when I get up. It can be a crippling pain when I stand up from laying down and it takes about 10 seconds to p. I have had a sonogram and the baby is in the right place. Any idea what this could be? It started about 2 weeks ago.