Stop taking chlorella, it can't help and can only hurt due to the high sulfur content.
I would suggest that you lower your dose, stop the chlorella, and do rounds that are 4 days on and then at least 4 days off after. If you are mercury poisoned you will need to add in ALA at some point, assuming you have had no exposure for 3+ months.
Also be sure you are taking the basic supps Vitamins C, E, Zinc, magnesium, fish/flax oil. These will make chelation a lot easier and less stressful.