How experienced a pistol shot are you?
If you are relatively inexperienced, the following remarks may be of some help.
If you're shooting low, it may be you and not the gun.
Usually, improper trigger control and/or flinch will cause shots to go low-and-left (for a right-handed person), but there are control issues which will also send shots low-and-center.
Also, the pistol's sights may be regulated for 25 yards, and if you're shooting a 9mm at seven yards, hitting low would be normal. (You'd hit high at 15 yards.)
Try shooting from a stable rest, or try letting someone with lots of pistol experience fire several shots. That should give you diagnostic information.