I'm a waitress and suffer a lot of leg and back aches. could magnesium as a supplement help that and also help sleep and bowel habits? how much?

Possibly: If, like most people, you are deficient in magnesium then it is likely to help muscle aches, insomnia and constipation; if you aren't deficient it won't help but also won't hurt; it's safe to try as it is not easy to test for deficiency. I advise 400 mg of magnesium taurate or glycinate. You can also try epsom salt baths. See http://bit.Ly/1dpai09 also eat more magnesium-rich foods (esp. Greens).