I had some really bad leg cramps that woke me up and could not be rubbed or flexed away. Not even by the strong carpenter's hands of my husband. My advice while one is happening... Get up, and walk it off. It's painful but works quickly, and it's not like you were sleeping through it anyway. As far as everyone saying you should get more potassium, I'm not sure. My midwife told me to take a liquid calcium/magnesium supplement each night before bed, and this REALLY helped. I haven't had a leg cramp in almost two months (I am now at 36 weeks), and my only sleeping complaint is the ache in my pelvis when I roll over in bed. The liquid supplement is the kind of calcium/magnesium that is easiest for your body to absorb. It is chalky, but not too unpleasant. The one I buy tastes like blueberries. Good luck, and I hope you get some sleep soon!