At age 16, what does watery stool for more than a couple days mean? what could it be?

Colitis: This type of colitis is probably a simple viral intestinal tract infection in your case and should resolve within several days without specific treatment except rest, intake of adequate room temperature fluids,avoidance of harsh roughage foods, And use of kaopectate (kaolin and pectin) as needed. Mild food poisoning is another possibility but the treatment is the same. See your MD if symptoms persist or worsen.

Loose stools:: Could be due to a virus (or other infection) or something you are eating or drinking, or an over-the-counter medicine or supplement you may be taking. Sucralose (splenda) and sorbitol (in gummy or jelly candies, breath mints or sugar free gum, or prunes) can cause loose stools. If this lasts more than a few days,get checked to find out why. Avoid caffeine, alcohol, recreational drugs, fatty foods