What Causes Blood In Stool?

Hello Dr. I am a 20 year old male with a family history of ulcerative colitis and crohn s disease (my mother and her brother). Recently i started to experience blood in my stool after alcohol (not much, actually very little amounts) and I am quite sure that I at one point had an anal fissure (whether or not the initial blood came from this). I suspected the horrible Crohn s, but now I m not so sure anymore, as I just noticed a kidney bean in my stool. I have not eaten any kidney beans for years. I fished it up, and pressed it, and it had some sort of membrane that came easily off, and it revealed a white/yellowish gooey substance inside, and I am now wondering - could this whole experience of mine be a simple parasite? Best regards