Pickle Juice. I know it sounds weird, but it really helps.
Leg cramps at night can be an indication of potassium deficiency. I had them with my second. I try to eat 1 or 2 bananas a day and that seems to help. Hope it's better soon but try bananas!
Sleeping with a cushion in between my legs really helped me :) x
Leg stretches. While sitting with legs stretched out have your partner push your feet towards you at the same time push your feet towards him. You can do this also when you feel the cramp coming on, just stretch your feet towards your body and take deep breaths.