How to make my son active and more energetic?

Hi doctor,

My son is 15 years old. He has an allergy problem and once had an episode of severe congestion. He was hospitalized and given inhalation nebulizer. Now, he is on inhaler Aerocort. He feels tired, panting on playing and often tends to sit while playing. He feels very hot on his ears, limbs and face. He has nosebleeds, acid reflux and complaints some problem with swallowing coconut. He is underweight. His height is 5'4". His sleep is not good and he wakes up on slight disturbance. He does not feel refreshed in the morning. He is not happy, fresh and energetic for his age.

Please guide me.

Thank you doctor,

He is always in a mood to lie down and keeps engaged in television, laptop and mobile. He has energy crisis, irritable, on edge and most of the time has to brace himself even for simple chores. His face looks ill and he always have phlegm in throat and feels some obstruction. He gets viral infection frequently and was hospitalized for viral infection three years back. He looks like he is carrying some infection, which is making him lethargic. His appetite is low and goes only for chilled shakes, etc. In food, he looks for taste and spice. Though we allow only home made food (though spicy), but sometimes he goes for burgers. He falls ill frequently, but these days there is no acute problem. His growth not satisfactory. Though lately shown some spurt in growth that is height only in 18 months. He looks very slim and sick. He is very intelligent and has willpower. Because of his will power, he avoids complaining to keep matters under wraps to avoid giving us trouble. He has weak backbone, so cannot sit too long. He is getting pain in neck, head and legs. His weight is 88 lbs and height is 5'4". He is under performer in studies, though mentally very capable. But, he is a genius in maths. In sports, he lags behind due to stamina issue. Lastly, he got nebulized six months ago on Aerocort inhaler. He does not use to stress himself often. We are also getting worried about this. Thank you doctor.