Hi C.. I breastfed my three childern and two out of three of them did the same thing at or around 4 or 5 months old. People that I talked to about that suggested that they might be having some mild form of pain in their gums since the little buds for their baby teeth are starting to form around that time. If that's the problem he may need to learn how to adjust his latch a little so that he's more comfortable. Also, to test the theory, maybe put on a little baby orajel right before nursing or try rubbing a small amount of children's benadryl (the pink/allergy one) on the gums. The most important thing is not to try to force him to latch on during those screaming fits. As hard as it is, sometimes you just have to wait until he calms down and then just try again. He will get the nourishment he needs even if he goes through a couple of hard days. Just faithfully offer him the breast and if he can't eat just then try again in another 15 to 30 minutes or whenever he is calm. You will definately want to protect those feeding times as soothing, relaxing times!! :)