I think that the premise that cilantro removes mercury in a few weeks is mostly a myth. People who make that claim probably never had much mercury to begin with.
You probably have it right about the cilantro raising your mercury levels. Cilantro mobilizes the mercury in your body but doesn't eliminate it.
Chelation is a slow process if you have high levels of mercury because your organs are probably damaged by the mercury, plus they have high levels of toxins to eliminate.
Forget about the cilantro for awhile and work on chelation. You can take cilantro again when your mercury levels fall.
In the meantime, you can also use herbs to cleanse your liver and kidneys to speed up your body's ability to eliminate the mercury.