For the past two months I have experienced change in bowel movements. Sometimes Thayer are loose, sometimes hard sometimes thin sometimes normal size. I have a history of gerd and generalized anxiety disorder. I do get cramps and sometimes vomit stomach bile when stressed. My question is on blood in stool. I don't know whether it's blood or undirected food. Occasionally about two times a week I will go to the bathroom and see a couple dark spots on my stool. I would not consider these to be tar like. I am 20 yes old and in basically good health. Had endoscope done with no visual signs of anything wrong. Have not had the colonoscopy done but since I am a big worrier I think I might have to. Now this may sound gross but one time I took a butter knife and cut the black part out and it turned out to be a black olive Im positive. But even when I haven't had black olives I sometimes see these spots. Any ideas