Very likely Terry is correct. If you're not getting your string arm elbow around behind the arrow, that is, in alignment with the arrow, then your shots will go left, because your forearm and probably your shoulders are aligned to the left of the target. If you think you are overdrawing the bow, it is probably because you are using your arm muscles and not your back muscles to draw the bow. When you draw with your back muscles, your string arm elbow does not keep heading back, causing you to overdraw the bow. Instead, it naturally curves around your spine in a J shaped path until your shoulder blade moves as far as it can toward your spine at full draw.