Three days ago, my four month old baby started spitting out all the milk. He is exclusively formuLa-fed (nan pro 1). He had been showing symptoms of a waning appetite before that. I started him on domstal baby drops (0.8 ml thrice a day), which helped in keeping the throwing up under control, but he completely lost his appetite. His milk intake went down from 900 ml a day to 300-400 ml a day. Today, we started him on walamycin suspension (3.5 ml thrice a day). His appetite has not improved. In fact, he threw up again today and spit out half of what he had taken. What is happening with him?