Welcome to HCM,
As he is having constant cough
and not gaining weight,he requires some investigations and after reports go for treatment accordingly.
At this age you should rule out,
due to worms,
3,Primary cvomplex as he is having constant cough and not gaining weight,
Go for ,
for ova avnd cust.
Give high nourishing food,Iron and multivitamin
More milk,pulses,eggs,cheese,dry fruits.
Ok and bye.