It really is confusing. I worry about a parasite being in my head also but it seems like there's no way to know for sure and who knows what imaging people look for on the tests, they likely don't think about a parasite being a cause of someones headaches and most doctors aren't too helpful with this. I have a feeling it could be a fluke effect too maybe, like a fluke hanging on so it's not wiped out with bowel movement and maybe that triggers a headache.