I bought my XDM 40 new a short while ago and I am having trouble with aiming it properly. I keep naturaly aiming low (about 2 inches) and when I try to compensate, I am 2 inches high. Its my first pistol so maybe im not squeezing the trigger right but I cant seem to find the sweet spot. Anyone have any tips for a novice handgun owner looking to improve on his accuracy?
I am deadly accurate with my Remington 870 shotgun so I know im not blind

I think there might be a fundamental technique in handgun accuracy that im missing completly.
(if its relevent... I'm a left-handed shooter.) Only issue with my XDM 40 is that it doesnt have ambidextrious slide release.