Why the hell can't i gain any weight?

I'm nearly 17, and i eat like a PIG every single day of my life, i must consume at least 7x as much as a normal person eats every day, and lately I've been wanting to get into shape, get a six pack and get some muscles, and as we all know you need fat to turn into muscle first, but i CANNOT gain any weight at all. Is it because my metabolism is near around 3x faster than a normal persons?

I also don't want to use any unnatural stuff to gain weight (Protein shakes, and creatine) Can anyone help me?

Thanks.