Don't know what it is, but it probably is not the only parasite, sad to say. Most parasites do not show up in the stool and you probably have others. See the cayenne pepper challenge test, for ex., in the link below to see if you might have tapeworms. Hulda Clark says everyone she ever tested had them.
The most important Q. becomes, not What the heck is it? but Are they gone or not? Great that you have a microscope though to check your progress for at least that kind.