A.S.
It is normal for exclusively BF babies to not poop very often (but when they do go....watch out!), BM doesn't leave much waste. But if he is grunting etc I would think he is probably constipated from the formula. If you can go without giving him that he would probably have an easier time. He may still go many days without a bowel movement, but he won't be constipated like that. With a baby that young, I wouldn't be giving him anything additional to help with the constipation.