Beanpole, do you want to know how to gain weight? Eat. You can blame it on a fast metabolism, and maybe it's true, but I doubt it. Skinny people only remember the rare meal where they go ape shit with the food. Most of the time, they're eating once or twice a day and/or eating very small portions. I was once that skinny kid too.

Whatever you are eating, it isn't enough. Otherwise you'd weigh more than 160lbs.

On top of that, you're 19. You have no business messing with any sort of androgen. And you shouldn't need to mess with them either. You're a testosterone factory at that age. I suggest you use what you have naturally, while it's still there.