If you are consistently putting the rounds in a very tight grouping, I would suspect the sights need adjusting. While it is true, as others have mentioned, low and to the left usually is an indication of jerking the trigger, in this case where the groupings are tight, I don't think that is the problem.
Find another shooter that is a consistently good shooter and give him a magazine or two to see what he does with the gun. If his rounds go low and to the left, good chance it is the sights. If they are well placed and in the center, go out there and work on dry firing your gun.
May the Schwartz Be With You.
NRA Life Member