What Causes Abnormal Bowel Movement In A Toddler?

I have a 2 1/2 year old that is having 5-6 smears of a bowel movement every other day just prior to having a large bowel movement and sometimes he won t go for 3-4 days. He usually pushes hard to have these smears and starts to cry at times. We have changed diet, cutting down on dairy, he eats 3-4 cups of fruit daily, prune juice and 3-4 prunes daily, 2-3 cups of water, he has whole grain cereal, and lots of exercise. can you give advice on having a normal bowel movement without the struggle to push and crying?