Flat? Mabe it was a liver or intestinal fluke? I have passed those critters, too. You can look at the pictures of flukes in the parasite section, this might help identifying what you had.
I don't think you would mess up a parasite cleanse by doing a liver flush( I have had no trouble with it).
But if you are already feeling week, perhaps the toxins the little aliens are giving off is all your body wants to deal with for now?
Wishing you much sucess!