Issue passing stool for 6-mo. i think it's ibs-c since my stool looks fine (no blood/tarry) & the symptoms seem to vary based on food consumption & sleep. history of colon cancer in family. almost impossible to pass stool sitting. hard while standing?

Why do you think you have IBS-C but not a simple, common constipation. You need to drink fluid well (2 liters a day), eating high fiber foods and exercise. Stress can affect bowel movement either way but more often causing constipation.

Your symptoms suggest constipation. You may take a fiber laxative like Metamucil and drink enough water daily so that your urine is colorless. For the long term you may try to increase your intake of fiber foods. Consult this site for fiber foods. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/high-fiber-foods/art-20050948 Wish you good health!