Well, it could be colon cancer, but it's more likely hemorrhoids. Everything you described, including the clotting blood fits. If you've been losing blood on and off for 2 years out your butt, plus your period, you could be slightly anemic. Is there some reason you are NOT talking to your doctor about this and asking US?!? The most important thing about colon cancer to know is that it's well treated if caught EARLY. If you have a history of people in your family who have colon cancer, you have a higher chance of having it, too, but 19 is pretty young. Still, you should just have it checked out. What--are you embarassed about talking to your doctor about your butthole? Think of your digestive tract as a whole thing with your mouth at the start and your butthole at the end. There--you aren't embarassed to go to the dentist, are you? Well, don't be overly modest about the other end. The doctor has seen it before. The exam is a piece of cake. You lay on your side on the exam table with one of those paper sheets over your bottom half, facing away from the doctor, pull your knees up slightly, and the doctor will do the finger/rectal exam with a glove and some lubricant. It takes about 5 seconds. No big deal, and you leave with information that solves the mystery. You can also have your gynocologist check it out when you go for a pap. A lot of gyns do that as a routine part of the exam. Call for an appointment tomorrow, and while you're waiting for your appointment date, would you think about taking a multivitamin with iron once a day? That will help with the anemia. Don't over do it--too much iron is as bad as too little. Now get going!