Is it worth getting into natural bodybuilding?
Good for you for declining to use steroids, especially at 15. Take a look at natural bodybuilders on YouTube. You can see those who've been told the same thing as you, started training properly and got good muscle size. Stick to the program, have patience, and give it time. Ignore those who encourage you to use drugs and ruin your health. As you train, surround yourself with natural bodybuilders who have experience and you'll achieve good success. Best of luck.