Poor, poor child

Poor Nathan is constipated. And if you don't wish to know about my child and his bathroom issues, please feel free to stop reading right now. I feel sooo bad because since Sunday he has been straining and he gets all tense and he SCREAMS and CRIES when he has to go to the bathroom and it is HORRIBLE to watch. My poor, poor child is so constipated that he can't do what he needs to do and he just strains and cries. I've called the nurse twice. Once on Sunday, and once today. We've got him on all the "P" fruits. Pears, pineapples, plums, prunes, and peaches. I even went out and got him Fiber One yogurt per the nurse. He's got his sippy cup with water and yet he's still making horrible noises when he needs to go to the bathroom. How in the WORLD do you explain this to your child? He doesn't understand WHY he hurts, just that he hurts. And he holds out his little arms and cries for "mama" when he's hurting and there's not a damn thing I can do other than change his diet and monitor him and hold him and try and soothe him when he cries. Why isn't THIS in the parenting manual?? And if it is, how in the WORLD did I miss it???