My daughter had similar issues, though not so extreme as to cause night time screaming. Anyway, we got the same advice to give her bananas. We did that and also had her do some leg stretches each night before bed. Toe touches for the hams, heel to bottom for quads, and standing on the steps, heels down for calves. This combination really seemed to help. She also was sensitive to the binding effects of bananas, so we made sure to include more high fiber foods in her diet. Oatmeal or raisin bran for breakfast, raisins and yogurt for snacks, honey is also a great, natural stool softener. Good luck!