High grade fever in this age requires an aggressive approach to locate the focus of infection. A fever running so long needs a work up for meningitis
as you mentioned there is history of poor intake. Tyohoid, malaria
and urinary tract
infections are differentials that require blood tests which have been done for your child. The condition has certainly worsened as he now has developed cough. So till a diagnosis is made, supportive care assumes a very important role now. This involves bringing down the fever with paracetamol
and tepid sponging as it may predispose your child to febrile convulsions
. Maintain adequate hydration and urine output. If he is not taking orally, give iv fluids. Ensure his blood sugars are being down frequently.
Wishing your child a speedy recovery.