small amounts of bright blood on the tp or a spot or two on the stool is usually from a hemorrhoid or anal irritation which can include a tear (anal fissure).A lot of people have internal hemorrhoids (so nothing you see or feel on the outside) and often do not know they have them unless they have been scoped and/or they start to bleed. So you can have hemorrhoids and not know it.If the blood is mixed in, especially if it is more of a brownish red rather than bright red indicates bleeding higher up in the GI tract.That can be from something acute (like a GI infection that is bad enough to get the lining that irritated and some things like a C. diff overgrowth that can be a little longer lasting but tends to occur after antibiotics), something potentially acutely dangerous like ischemic colitis where part of the colon may die (even if most people recover just fine, this is pretty rare, but if you start feeling really bad or there is a lot of blood go to the ER, please) or something chronic like ulcerative colitis or crohns.IBS by itself will not cause bleeding, but the issues with constipation or diarrhea can play a role in setting off/irritating things at the outlet that can bleed.Your colon does NOT absorb the majority of your nutrients (a few calories and nutrients can be released by bacteria in the colon but by the time the food gets there you are done with it).People who have their entire colon removed and so food goes straight from the small intestine into a bag outside the body absorb all the nutrients and calories they need from their food.IBS is a problem with the colon. Transit and absorption in the small intestine is normal/near enough to normal to not cause a problem. If you drop weight all out of proportion to what you eat that indicates a disease in the small intestine like crohn's or celiac disease and neither of those are IBS.When you say cancer in the family do you mean one or two relatives got colon cancer when they were in their 50s or older or do you mean about 1/2 of your relatives got colon cancer under 50 (usually in the 30-45 age range)?Colon cancer in elderly relatives does not increase your chances of getting colon cancer under 50. If 1/2 your family gets colon cancer by 45 or so you have a familial disease (genetic) in your family that causes people to get hundreds of polyps in their teens and twenties rather than a few after middle age. At minimum I would get the anus looked at to make sure there isn't a fissure (as some can need medical treatment and not just over the counter ointments). Have a stool test to see if you have something in there that needs to be killed off and a complete blood count to see if your inflammation markers are elevated.If the blood and stool is normal and the blood is bright you may not need to have to pay for a colonoscopy.