yes you are natural, simply because you have almost no mass, you re just lean. You do a lot of sport, maybe basketball or soccer which keeps you with very few fatness, are genetically an ectomorph -whatever you eat you never get fat- and lift often and only eat proteins and some cheat meals here and there without caring much about nutrition. Nobody can say you re muscular as long as you wear a tshirt, whores only look at you when you re shirtless. Been there, done that.
