Many people, including myself, have had your same experience regarding lab tests for parasites. I don't think, personally, it matters terribly - though it is interesting - what kinds of parasites they are. Just so they are gone. It does help to know one isn't just seeing undigested food bits though - so the pictures can be quite helpful here on the CZ gallery, & elsewhere.
Here is what has helped me in case it can be of any help to you.