HI. The symptoms of vomiting , pain in the abdomen and pain on walking is definitely an indication for investigations: I would advise you the following: Take him to the Pediatric Surgeon to get a physical examination done to get a clinical diagnosis , to be supported by ultrasonography, blood and urine tests and stool tests. It may be due to : -Tummy tonsils- meaning enlargement of the lymph nodes of the abdomen. -Appendicitis- by default this has to be ruled out in every case of pain in -abdomen of a child. -Worms. The best diagnosis is a high resolution ultrasonography. some blood, urine and stool tests. A therapeutic trial with a course of an antibiotic, metronidazole and probiotics under the guidance of a pediatrician / Surgeon always helps to solve the problem and to get a diagnosis. Also given is a dose of medicines active against worms in intestine. I hope a consultation with a Pediatric Surgeon, investigations and a course of an antibiotic and metronidazole should solve the problem. If this is indicative of appendicitis , please go for the surgery of appendectomy.