What Causes Dry Stools With Spotting?

I'm a 39 year old male with no history of smoking or drinking. Almost 3 months ago I passed some dry stool with a (little bigger than a drop) of wet blood on the end. A day or two later diarrhea started and lasted over an month and a half and I didn't eat much because everything turned to liquid....some foods made it worse others not so bad. Dr tested my feces and nothing showed...was told to try fiber which worked but bowels aren't right still. Lost 14 lbs in last almost 3 months with very little pain. Had a abdominal ct that showed no obstruction though I'm passing a weird mucus now on my stool..I read a lot about what this could be but I'm really scared it's cancer.