I have thread worms for the 4th time in 3 years what do i do?

Good hygiene: Thread worms (pinworms) are passed on by poor hygiene, not washing your hands after using the toilet or contacting objects contaminated by the worm’s eggs (underwear, bed sheets, towels, etc). Dirty fingers are put into the mouth; then the eggs grow into worms in the intestines. They can be treated by your doctor, but good hygiene, including laundering is the only way to keep them from recurring.