In some cases, our body frame and mass remain the same no matter what we eat, for as long as you eat right and you're healthy (for ex: not sluggish) then you're okay.
And try Appebon tablet 500mg! or maybe visit your doctor and he prescribe you some supplement that better suit to your body need sir.
It's important too that you do some exercise. maybe what you need is just to bulk up in the right places.