Years of researching and I came across a interesting Nematode that looks exactly as what I have have going on and have seen, I remember reading how it travels in the environment through what is called a sheath I believe. I see the same thing you have described in my toilets before and found the info from some .edu site called Rootknot.
I also found that Rootknot matches everything I have been seeing in my stool and even pictures on this site. The only thing is, Rootknot are plant eating Nematodes which get big enough to see which has been documented infecting a person in the 1960's I believe. It's on the CDC site somewhere.
I got sick and I know that I lived on a Lake in So Cali and a few days after I broke out in hives and went to the ER a few Dozen Mallard Ducks died in my back yard which was the lake.
I also keep trying to grow Lotus from a seed and once I touch the water, it all starts to die from what looks like rootknot. It is the craziest thing but than again there are tons of parasites that can live freely in water so maybe not so strange.
Rootknot will grow in our yards, soil, lakes and float through the air. You can plant Marigolds flowers to kill them. Even if it isn't Rootknot which I have no clue, it is a good idea to plant Marigold all over the yard to maybe kill all Nematodes.