Google "walkback tuning bow" or something of that kind and I'm sure you will find the solution to your problem. Bronco has a point as well, and if that's your problem, then luckily it's a very simple issue to fix.
Any bow sight can be made to shoot POI=POA at one range, and even be incredibly accurate, but if your tuning isn't right, then you have "crossing lines" issues (line of sight vs. arrow flight makes an "X") such that at closer ranges, you'd hit left, at long ranges, you'd hit right. Measuring your centershot doesn't do you any good if the plane of your string travel doesn't cross through "13/16in centershot," measuring only gets you close for a starting point. If you "walkback tune" your bow, or basically tune as I described in my first post, you'll find that you eliminate that misalignment between line of sight and line of flight.
Shooting improperly cut arrows, improperly timed cams, improperly spined shafts, improper point weights etc will diminish accuracy, but seldom will it create a regular drifting issue like what you've described - especially if you have an ideal tear on paper tuning.
It's not that complicated.
Last edited by Nomercy448; 12-22-2014 at 06:13 AM.