So... I have had zero blood in my stool since. Until yesterday I had another hard movement and there was one small streak of blood. Same thing tonight. Hard movement small streak of blood. What does this sound like????? If it was cancer would the blood stop for a month? If it is cancer how curable is it in a 21 year old???
Having pencil thin stools 3 times in your life will have nothing to do with what you have now. In fact most Cancer Registars say that Pencil Thin stools is somewhat of a myth. That most symptoms are bleeding and constipation followed by diarrhea.
More than likely you had an anal fissure or perhaps even some hemorrhoids. Especially with your age. However, with that being said, it would never hurt to go to a doctor and let them do a fecal occult test, to check for hidden blood and make their own diagnosis. Im going to put my money on the simple fact that you probably just had a tear from a painful bowel movement and nothing more serious.