Is this the first time this has happened? If so, did you eat anything out of the ordinary in large quantities? If a breastfed baby is sensitive to a particular food, he may be fussy after feedings, cry inconsolably for long periods, or sleep little and wake suddenly with obvious discomfort. Reactions to certain foods may occur within minutes, but symptoms in breastfed babies usually show up 4 to 24 hours after ingestion. If baby indeed has an acute reaction to a new type of food, or to a food that mom ate a large amount of, then he will probably be back to normal within a couple of hours. If this happens persistently, then best to approach doctor and try to narrow down what exactly baby might be allergic to.