hmm, sounds like they COULD be fluke worms-- as the ones I've seen are brownish-but opaque so you could see through them.
Are they tapered on each end? If so, that's fluke probably.
There are so many types of parasites-- the medical schools have most of them catagorized, but your average doctor isnt aware of all the thousands of them unless they spent $$ on parasite courses in Med school. Most people in med school will not waste their time on such courses if they are not necessary for thier credits to graduate.
Also- with all the traveling back and forth now with cruises and such that we Westerners do-- we bring in new species of parasite eggs into our borders without knowing. Many adapt nicely in America and Canada. Some are brought in from tropical fruits-- which is why it is so important to really scrub your produce- and cut off any areas of the fruit/veggie that have any type of disfigurement or cut or knick. Get that Veggie Wash , and soak things like parsley and lettuce in water mixed with Apple Cidar vinegar for about 20 minutes- then rinse with water.