This could be worm infestation ? Thread worm ,spreds through contamination .but other worms may be there so see a doctor and get stool examined.If required some blood test
may be done. Deworming may be by Albendazole
4oomg 1 tab at bed time may be repeated after 1 or 2 week. Take care of your diet and water intake. Do you take non veg food as they can hve specific infection like Tape worm.