I have gone through your question. It seems your son is having food poisoning
which usually starts with vomiting
followed by fever then somtimes loose motion
few times. Accompanied symptoms are little headache and stomach pain.
Food poisoning symptoms subsides within 48 to 72 hours on its own. I would suggest you give your child Syp Emeset and Syp Gelusil
MPS[ Antacid] 5 ml 3 times a day. Light and non oily food will help.
hope i have helped you.