the past 2 months i have been having pain from bottom rectal area through the back coxix area going up to my back both sides including my front and side abdomen . My stool has been dark and small marble like stool. I have not acutally seeN red blood though.It has been hard to go, i also had prostitias in jan. i did get my kindeys checked, i did also get an mri of coxixs and finally e-room last week cat -scan with the injection fluid. They Found something but they were not sure, possible again its possible-rectosigmoid cholitis. Please provide me with some info, why does this happen? At this age? I am getting colonoacopy with biopsy as well.should i get a stool kit from the lab.