If you have hard stool and eat fiber and drink water and exercise, the question is how much fiber and what type of fiber ( soluble or bulk forming fiber) and how much fluid do you take daily. To prevent constipation your body needs 2 quarts of fluid per day (8, 8 oz. glasses). You also need 30 to 40 grams of fiber daily. If you are taking the proper amount then you might have been constipated, packing up a little stool every day if you don't have quantity sufficient stool output based on the amount of food intake you have daily.
If you have gradually packed up with stool I would suggest that you do something to clean out the formed stool in the colon one time, by taking a bottle of Magnesium Citrate if you kidney function is OK or take an enema to clean out and then go back on your program and see if it works OK for you. Then set an expectation for frequency of stool. For example if you eat 3 big meals per day, then expect a bowel movement (BM) every day, if you eat 1/2 the normal, every other day and 1/3 the normal, every third day. On the day you expect a BM and you don't have a BM by 4pm, drink 4 oz. of prune juice followed by a hot liquid. If you don't have a BM by bedtime, take 2 Tablespoons or 2 caplets of Milk of Magnesia and you should have a BM after breakfast the next day. If you have to repeatedly take MOM, then your bowel program is lacking something. Check to see if any of the medicines you take have constipation as a side effect. If so you will need to change you bowel program to accommodate those medicines. (ie. if you are on diuretics, you may need to take a stool softener to hold fluid in the stool to prevent it from becoming hard.) Also, if you are on Narcotics or Zofran, you will need to take a stimulant laxative along with a stool softener (Senna-S) titrated up to 8 per day as needed to promote regular, soft, formed stool.
If you are not taking adequate fiber, you could either take one tablespoon of Metamucil or Citrucel in 8 ounces of water and immediately follow this with 8 more ounces of water. The amount of water with the fiber makes a big difference. Or, you could eat one cup of Fiber One cereal (the kind that looks like noodles) and with fruit on top of it, you are getting your normal daily intake of fiber. Any additional fiber you eat will also contribute to good bowel health. This gives you the amount of bulk forming fiber that your body needs for regular elimination. Soluble fiber (ie. Benefiber and Fiber Choice) provide fiber but not the bulk forming type that will have a better impact on regular elimination.