Try to visit ur family pediatrician. Viral fevers are rampant now and to prevent this take all necessary measures from mosquito bites.
It's better that u consult good pediatrician nearby and get investigated as u are saying he is not eating anything and became thin.
Next Steps
Malnutrition-infection- is never ending cycle. Take necessary dietary advice if ur child is under weight.
try to know the root cause why he is having fever maybe play school if he is going or under weight or anaemia or something else. and take adequate treatment.
Health Tips
These days climate is changing and continuous rains adding to that we should be careful to protect our children.