yes it will screw this up for you. Not sure HOW BAD var will, but the point is I think you need to do NO drugs and just focus on getting your training correct like I said.
I am in medicine so that's why you haven't heard that before, most people wouldn't know that info.
Here's some motivation. I at 26 had 500lb bench, 315 shoulder press, 20"+ arms, 240lbs weight, big delts, legs etc. When I started I was 150lbs (at 18). I never used drugs to do it, it was just busting my ass in the gym. So it can be done. I still am not that far off those stats to this day. Go train with some powerlifters, you'll see how they're built and pick up much training info.
Please no drugs at your age. I don't know how many skinny 18yr olds ask me about drugs because they're in such a rush, be patient and get to the gym.