It sounds like your pelvic joints are loosening ready to stretch to accommodate the baby. Did you know that the pelvis is not one solid bone? Its normal but if its painful them talk to your midwife or doc...you make need to be a bit more careful about what you are doing.
I'm 27+2 and I haven't experienced this yet. I've had the most unimaginable bloating in recent days, despite eating no carbs. Each day has been an uphill struggle if I'm honest.
Congrats NoMercy - hope it eases, ive been pretty miserable the last few days with stomach aches and generally feeling crappy. Must be a 27 week thing.
I had it with my middle child. Turning over in bed and then walking. Walking was very very painful to start with but eased up with each step. It's very painful and not much could be done (things might have changed)
It's always best to see your midwife though.
Sam - most of the aches and pains come in later pregnancy.