Lower back pain

I'm 31 weeks with my baby girl, and I sit all day. I try to get up and walk every 10 mins but I work at a medical office so I can't really walk away from my desk. But it's right above my hip and pain shoots down my right leg. I have trouble laying down at night to go to sleep with it too. The pain makes it hard to walk/lift my toddler/ work the long hours that I work. Anyone else have this pain? I hate to keep bothering my OB. This pregnancy and me have been having one problem after another since month one.