I'd really need to see you shoot. I didn't really model my jumper after any sharpshooter/pureshooters(I actually modeled it after Kobe's) but what others are saying pretty much is universal. You always want to make sure you get a good lift from your legs, and you also want your upper torso strong. Fatigue plays a factor, and you need to be able to use both when the times comes. Make sure your back is straight as a board as you reach the peak of your jump.
Keep your elbow bent at a 90 degree angle at all times, and make sure your wrist isn't stiff. It should be slightly bent backwards, and you should be able to slide a finger in between the ball and your palm. That way when you release, you're able to add more rotation when you snap the wrist towards the rim. Your index finger & middle finger should be the last two fingers that touch the ball as it's leaving your hand, and make sure to follow through.
Something that can drastically improve your shooting percentage is ball position. What I mean by that is, you should be able to see the hoop with both eyes at all times. A lot of guys shoot with the ball covering one eye, and don't even realize it. When I was kid, I had that problem. Watched an old Pistol Pete film, and dude brought it to my attention. Personally, I'm right handed, so in order to break that habit, I would stand in front of the hoop(maybe five/7 feet away) and cover my left eye before I shot. At first, all I saw was my right arm in the way of the hoop, so I slightly brought it over where I could see the rim at all times and took shots. It helped tremndously, and you'd be surprised how many cats make that mistake. A video of your shot would be great, but I could understand not wanting to post it.
