Try sleeping with a thick pillow between your legs, if your a side sleeper, I have it bad in lower right leg.

Something else is causing it, most likely back issues. Find the problem and start there. A roman chair (look it up) is used to strengthen the lower back muscles to keep your back from shifting. As many will agree, there it no medication to mask the pain. But keep moving around, the worst thing for any back pain is to sit still.