My son passed somewhat hard stool today for the second time.he's on formula feed. Most of the times, he doesn't want to feed the formula and keeps on crying and put both the hands inside his mouth. He's hungry but doesn't want the formula. Everytime, I have to make him sleep and feed him while he's asleep. What could be the reason behind this? How much water per day can I give him in order to avoid constipation?