Were you under the care of a doctor/naturopath? Constipation may have been a result of mineral imbalance brought on by chelation, but, I gather, that constipation was already an issue given mercury toxicity...
My understanding is that continued chelation may be ideal, but getting your system back in balance must come first. I suggest taking a quality multi vit/min and a trace mineral supplement containing fulvic acid, like Morning Star. I would also avoid distilled water, if you currently happen to drink it, to ensure that you get even more minerals into your system!
I would also avoid any cleansing until you get your minerals balanced.
Chelation is really tough on the body.