My ob recommended Blackmores' Bio-Magnesium tablets and after taking them for just a day my cramps stopped completely. I kept taking them until almost the end of the pg and never had another leg cramp.
Blackmore's Bio-Magnesium has kept me sane! Not a pregnancy symptom for me, but a sufferer of restless legs/night cramps. At my worst I wouldn't get more than 1/2 hour sleep in a block. I can SO relate to wandering around a dark house, so tired I could drop, to try to get my legs to settle.

It was a nightduty nurse that put me onto the magnesium. She rustled some up from somewhere in the middle of the night and the relief was practically immediate. Some were ordered for me from pharmacy the next day & 15 months later I swear by them still. She laughed when I wanted to hug her the next night ... apparently I'm not the first and wont be the last to react this way

The other thing that was recommended to me (and this is a bit out there ) was to put a bar of plain bath soap (not dove or one of the moisturising bars) between ur bottom sheet & the mattress down at your feet. I have never been able to find why this is supposed to help, but it did seem to give me some relief. Crazy I know!!

Bananas are anther possible treatment. Potassium deficiency can be a cause of muscle cramps and bananas are a great source of potassium.

HTH and you get some relief soon, I do feel your pain