I started training at age 15 (6' tall) at a whopping 123 lbs. In two years I was 210 lbs. By 19 I was 240 lbs. I definitely had more fat on me than I should've but I was by no means a fat ass either. I never touched juice til my mid 20's. It was nothing but food and heavy ass weights for me. I ate every two hours, no matter what. Bags of peanuts in class, a gallon of whole milk a day, a shitload of ground beef, beef burritos, spaghetti....in other words FOOOOOOOD! Just learn to live with something always in your mouth and go insane in the gym. You'll grow, no doubt.
Of course I'm a major ectomorph so your metabolism may not allow for the insane amounts/types of foods I ate, but you get the idea.