Just gotta say I'm proud of you man. Your dedication is paying off, and will continue to pay off into the future. You are 15 and already looking great and lifting some pretty good weights. You keep training like you have been, and learning from the great folks here, and you are going to be far ahead of where many of us are by the time you're even old enough to consider the other kind of 'supplements'...and then if you ever do...wow!
Seriously, (even without considering your age...which makes it all the more impressive) your dedication to lifting and to learning...and keeping up with your training log are an inspiration to me, and I'm sure to many others here.
Awesome job man, and keep up the good work!
And one last thing, if you carry over your dedication to constant improvement and to constant learning to other areas of your life (education, and then career, etc)...and I'm sure you will, then I think you are going to be one hell of a successful guy in whatever pursuit you choose.