I shot very low the whole time, only managing to hit the center of the target 3-4 times. I'm not sure why.
Maybe you're still a little shocked by the recoil... so as you squeeze the trigger, you're probably anticipating the discharge and jerking the trigger just before the point in the pull where your brain knows the BANG is going to come. You might be closing your eyes briefly just at that point too, otherwise you'd probably be able to see the muzzle as it dips down a bit.
The trick is to pretend you don't know when the BANG is coming, and to just hold the sight picture as steady as you can.
Some people do a lot of "dry firing" with an unloaded gun to overcome this... Like even while you're watching TV, for example.
Just be sure to read what your manual says about dry firing. With some guns, it's fine... with others, it depends.