What are a reason i have blood in my stool and i go #2 about 1time a week?

A lot to answer...: Evaluation is always appropriate for bleeding from the gut. Black stool often means bleeding from upper GI tract; grape jelly stool from small bowel; silver stool from biliary tree; burgundy stool from right colon; red blood from left colon to anal canal. Re: constipation, rule out metabolic causes (thyroid/ adrenal), slow vs normal transit, obstruction/stenosis, inflammatory, rectal/anal problem.