It could also be your grip on the string. If you're not relaxing your string hand, you could be torqueing the string. When you relax your bow hand, does your bow have a tendency to move toward the vertical? If so, you're not relaxing your string hand. The way to relax your string hand and forearm is to draw the bow with your back muscles rather than your arm muscles (easy to say).
As was mentioned earlier, if your eye is not over the arrow, you will tend to hit to the left. Watch the flight of the arrow. If it seems to be moving toward the target from the right to the left, then your eye is to the left of the arrow. If your eye is over the arrow, the arrow will seem to fly straight toward the target.