You could be torquing the handle. Make a U with your thumb and hand and cradle the bow into it, but don't actually hold the grip, just let the act of pulling the string back keep the bow in your hand. The put your middle finger across the front of the grip for stability, but don't apply pressure. Make your shot and catch the bow with your middle finger by squeezing it down after you shoot. By keeping as little finger pressure off the grip when you shoot you'll overcome anyy sort of torque issue you could be having.
I am not a seasoned professional. I know that when sighting in a rifle you sometimes have a similar issue.
The issue is easily solved by moving your sights slightly. I would think that moving your pins to the point of impact might be an acceptable solution as well
You could also be squishing the string into your face. I do this sometimes and it will move the arrows to the left. Also like was mentioned you can move your sight to the left.
Try moving the pins to where the arrows are actually hitting. If you are still hitting to the left then it probably is a form issue. If not, problem solved.
Sounds like you have shot the bow long enough you might have some string stretch going on. It would be worth a trip back to the pro shop and get it paper tuned while you are there. You should be able to hit small bulls eyes at 10, 20, and 30. If you start shooting far left after those ranges it's typically the shooter.