Hello Prashant,
Its indeed sad to know about your health condition but you seem to have a weak constitution. In your case, more than medicines you need a good nutritious diet and lifestyle modification to boost your immune system so that you don't fall ill easily. Usually children who have a weak immunity fall ill frequently during childhood which hampers growth. That is why you are probably so lean and lean people are at a risk of getting infections easily.

Persistent cold and sinus problems lead to premature greying of hair. You have difficulty in concentrating due to your sinus problem and also because you seem to be malnourished due to repeated illnesses.

I would suggest you to focus on building your immunity by making a few changes in your diet.

Have a nutritious diet which is easily digestible, that is don't eat too much of deep fried and junk foods, but rather focus on having easily digestible foods like rice, chapatis with a little oil/desi ghee smeared on them to increase calories. Dals and beans like rajmah/chhole and if you are a non-vegetarian then you can have whole eggs either boiled or as omelettes, mutton, chicken etc. Include fresh fruits like bananas, mangoes, grapes, oranges and papaya in your diet. Have different variety of vegetables, leafy ones like spinach, methi or fenugreek, ladies fingers, jackfruit etc. including root vegetables like arvi, potato, yam etc. Include dairy products like milk/curd/cheese in your diet.

Have a good filling breakfast which is very important if you want to boost energy levels and immunity. Your mind will work better when you have a good breakfast.

Sleep well for 6-8 hours at night and do some deep breathing exercises in fresh air outdoors. This will help to strengthen your body and you will feel fit as a fiddle. I hope you will benefit from my advice...do let me know if you need any more help. I will be glad to help you. Take care.