Hey hun, I have been taking 2 magnesium tablets a day since about 8wks along as well as drinking a glass of Indian tonic water (yukky stuff) before bed but I am doing this for leg cramps/restless legs. Lately I have been a bit slack in remembering to take the tablets. I started getting BH around the same time you mentioned and this time they have definately been different to last 2 pregnancies. I would imagine I would have to take a really high dose of Magnesium for it to do anything for the BH but it works for my cramps.

I know not much help for you but just my experience so far.