Leg cramp!!!

So last night my whole entire right leg began to cramp up. When I say whole leg, I mean from ankle to the bottom of my knee, then from the top of my knee to my hip. I had trouble falling asleep. I went to bed at 2, and now I’m up at 7 and my calf is still cramping really bad. I did no crazy exercise yesterday, and I’ve been drinking the same amount of water that I usually do. And I’m on my period, with 3 days left. But I never get leg cramps on my period. Why is this happening??