I am alternating between pebble stools and normal stools all week, sometimes on the same day. had a digital rectal exam in february and nothing was found. otherwise, i feel fine. ibs? colon cancer? should i be worried?

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!

Occasional dry stools and lack of roughage in diet can cause 'pebbling'. make sure you drink plenty of water and have some roughage in diet.