Whole body burning

Does anyone have a clue as to why I am experiencing a burning sensation all over my body? I have chronic fatigue syndrome. I've been doing some very good therapys this past year, to include ultra violet light blood work, glutathione IV's, and currently chelation for mercury. The burning has been intense the last several weeks. I was taking Niaspan at night, but have stopped that, as one night after doubling dosage per doctors orders nearly had to go to emergency for the burning. That was over a week ago. I feel body weakness, tremors, and burning. I've had the tremors for over a year. I have had MRI to discount MS. Any thoughts would be deeply appreciated.

God Bless,
Sara