I've always been prone to cramps and pregnancy sends my crampiness mad. The best thing, especially if you have a cool floor like tiles or floor boards is to get out of bed ASAP and place your foot flat on the floor. This willl usually help ease the cramp. And it does feel like a pulled muscle after

Also always make sure if your calf is red or swollen you get it check out to make sure its not a clot.

I hope you feel better soon