An old wives tale for leg cramps is to put a bar of soap under your fitted sheet next to your legs! It sounds crazy, and silly, but I have not had any since I did it :-)
Iv tried stretching befor i go to bed but it doesnt seem to make a difference :(
I don't know if it will help but maybe eat some bananas... They are supposed to be good for regular muscle cramps (potassium), maybe it will help pregnancy ones!
I know how u feel :( fortunately I don't go through it all night but almost every morning they wake me up!!! If I'm on my feet too long I get them too, quite annoying and painful. At first I didn't know what to do but sit through them, now I immediately stretch them out when I get them. Just remember to always flex ur feet and not point them and I try to do stretches everyday that tend to ease any soreness I get from the cramps. It's just one of the "wonderful " effects of pregnancy.