I realized that I have worms in this way; medical tests always shown negative for worms.
Read Hulda Clark 's book: the cure of all diseases, where she says about identification of these worms.
After 18-months, I'm still battling to clean them completely. Yes, rice grains could be tapeworm. Black-Walnut is effective for them. Zymex-II would digest them (worked for others, I'll still taking to clean it).
There could be Ascaris, thread worms etc. Take the right protocol. I'm taking Doc Sutter's protocol, which has helped the most so far (after trying Dr. Clark's protocols and Humaworm, which didn't work it seems)