I see white and yellow spots in my stool. but there's no itching... is this most likely undigested food rather than worms?

Mucus on stool: Mucus discharge occurs in up to 50% of patients with irritable bowel syndrome, with or without pain. Mucus may also be produced in response to partial obstruction, chronic constipation, rectal dysfunction, infection, ; even from secretory villous tumors of the rectum. At the very least stool studies ; probably a sigmoidoscopy should be considered, but a more extensive evaluation may be warranted.

Hard to know: You could have a stool sample checked -- it's hard to know without this kind of exam. See your physician about it.