I do not know anything about mercury poisoning, but I do about chronic fatigue. Did you know that hyperventilating causes fatigue, muscle weakness and numbness and tingling. THese symtoms in turn make the hyperventilating worse and it becomes a viscious circle. IF I remember correctly the hyperventilating overloads the body with carbondioxide, so that not enough oxygen can get to the tissues, hense the tingling, muscle weakness. It is know wonder this causes tiredness.
Hyperventilating is subconscious and you will therefore do it while sleeping. It is just a reaction to feeling stressed out all the time made worse by feeling tired and worrying about your health. If you have numbness of the lips , then that is a sure sign that , that is what your problem is.
You could try taking St John's Wort. This has helped me alot. YOu must use a potent brand like Kira as many of the others are not effective. If hyperventilating is your problem then this should work within one week to two.