[HELP] Jumpshot

I'm a 13 years old, 6' 2" and a big man (power forward, center). I play good defence, I'm good in the post, and I'm decently athletic. There's only one thing holding me back. My jumpshot. It doesn't matter where I position my hands to start, how high or low my release point is, what kind of angle my body is to the basket, I'm still inconsistent as hell. So, could somebody give me some good ways to fix my jumper that would be great.