If i have blood in my stool, but it's not much blood, should i be worried? what could it be?

Blood in stool is abnormal and must be investigated by a physician or a proctologist or a colorectal surgeon. If it's only a tiny amount of fresh red blood with no bowel symptoms an office exam is all that's usually needed as hemorrhoids or anal fissure may be the cause. At your age a malignant tumor is very unlikely. If lotsof blood mixed with persistent&frequent loose stools,see gastroenterolog

Any abnormal bleeding needs to evaluated. It may be a simple issue like hemorrhoids, but bleeding from hemorrhoids can result in anemia. It would be prudent to see your doctor. Wish you good health!