You may be suffering from Aspartame poisoning, see at http://www.sweetpoison.com/aspartame-information.html and other sites. It can and will mimic Multiple Sclerosis (MS) in some cases such as mine, that is where I found the problem to be with me.
I am completely free of cramping in my legs but am still researching cleansing my body of all toxins.
You must eliminate all foods with the above substance in them...all diet foods, drinks (sugar free products) and sweeteners.
Change your diet to natural foods (no processed foods of any kind).