S.M.
Even though I breast fed, my daughter has had problems with constipation since she was about 2 months old. Every time she needed to have a bowel movement she would shriek in agony. The pediatrican recommended 2 ounces of prune juice with 1 ounce of water. Once in the morning and once at night. This helped tremendously. At about 8 months old I was able to reduce it to once daily (same ratio). She is just over 10 months old now and doing much better. She usually has a movement every day that is soft and easily passed. A HUGE improvement to the shrieking. Good luck.
S.