GSM,
In order of probability:
1. Mashing, if shots are low and left and your are right handed, cure = seek good instruction & go "dry" to get rid of mash/anticipation.
2. To little tigger finger which is pushing the pistol left as trigger is pressed. Cure = install short trigger
3. Sights are off. Make sure front sight is centered on slide, if it is then move rear sight to the right.
Good shooting,
Dean