A Small Leg Problem?

I Am 5'6-5'7 135 pounds and I have the skinniest legs in the world I think. Everything else on me is a nice size, but my legs seem like they just dont wanna grow. My grows more than my legs. How could I get my legs bigger and to be the correct size for my weight and height.?Cause im tired of these bony legs I have. Oh and how do I add shape to them cause they dont have shape to them at all.