After I take a dump, I usually see little white squirmy worm things in my poop. What could be causing this?

Parasites are likely. Thread worms, aka "pin worms" are the most likely answer. There are other worm-like parasites but most are pin worms. More common in children less common in adults, most likely in all ages. There are medications to rid your body of these parasites. They cause rectal discomfort and itching, can wake children at night when pin worms are most active. Stool samples confirm diagnosis.