Talk to Pediatrician on Vomiting And Fever

My baby 27 days of age is vomiting and his belly seems like filled with air but feels soft when touch. Baby was fine before carrying circumcision at 23rd days of his age. No vomit and no fever. After that days he got fever and started vomiting by spitting out all the mother feed. By giving Panadol after every 4 hours fever is in control but he still vomits and seems uncomfortable. Quantity of vomit is quite large and point of worry for us. With 27 days of age what can be done?