I was thinking about your problem more.
I would have my testosterone levels checked. You can do this at the same places you do a piss test for drugs (Quest Diagnostic ) for example.
If you find you do have high testosterone levels, I would take advantage of what I have. I’d also develop some additional body mass and strength/power without getting hurt.
At 19, you can start looking at strength training. Strength training coupled with a diet hi in protein, and amino supplementation.
I would avoid anything that tampers with the endocrine system with the exception of estrogen blockers. When test goes up so does estrogen, even if it’s naturally. If you have natural hi test, I wouldn’t chance messing it up by injecting something external.
I’d also have well balanced diet which includes all the foods that are said to keep natural test levels up ( good fats, nuts, spinach, broccoli, zinc )
I’d look at limiting estrogen using an estrogen blocker for a year maybe two, while you are at this higher levels of natural test.
A good way to start adding the mass, is to work with a power lifting coach and hit the basics. Pay the money, and get your moneys worth. Also adding some explosive movements, such as Power cleans won’t hurt.
The goal is developing a base of strength and muscle that you can keep most of for the rest of your life.
I’d spend a minimum of two years going after the heavy basics, AND working with a powerlifting coach. Coupled with a diet hi in protein and aminos. Later in life, I would do at least 3-4 months of powerlifting focused workout to maintain and gain additional strength.
The goal of most of us is to work hard to put together a nice physique that can be kept with a reasonable level of maintenance.
Work your core. I look at the core like young guys look at working chest and biceps.
The core is the center of your physique. Some call them your sex muscles. But these muscles are crutial to almost any atheletic endevour, and even in every day life will allow you to live a better life. Core training would be 3-4 excercises on abs 3-6 sets every other day or twice a week. The same for lower back, and oblique/transverse abdominal work ( twists, rotations ).
With a stronger core, your squats ( front and back ), deadlifts, actually so many movements will be much stronger by removing the “floppy” middlesection ( even on a skinny guy ).
Do not get fat. Your body likes to maintain balance, and if that balance is fat, it will try to preserve it. Stay active. And stay somewhat lean.