I eat like a normal person but im still skinny. I want to gain some weight. I also hav astama problem so I can't eat heavy food. What should I do?

Workup. Your physician may think it's worthwhile to check you for malabsorption / maldigestion (celiac disease, mild cystic fibrosis -- the latter's a thought with your asthma symptoms) if you truly can't gain weight eating. Or you may be light-framed but still able to muscle up -- here's brad pitt at your age, slim, fit and no body fat. Let your physician guide you, and good luck.