I have been experiecing acute pain and cramps in my lower right abdomen. also have been passing black stool. i am worried it could be symptom ofcancer?

See a doctor: Any unexplained abdominal pain should be professionally evaluated, and so should possible intestinal bleeding, which is often the cause of black stool. At your age of 19, cancer is a very unlikely explanation, but there are several other possible causes, some of which could be serious. Don't screw around with this; see a doctor soon. Good luck!