Check your trigger squeeze. Dry fire and see if you can tell if your barrel moves when the hammer falls. If you are pushing on the trigger, your barrel will move to the left, like wise if you are pulling on it, it will move right. Using the very tip of your finger is fine, but you may have to move your finger in further if it takes you too much effort depending on your trigger weight. You should be able to take up slack, and pull the trigger straight back.
Dry fire, and talk yourself through the fundamentals while you do.
Steady position, check...
Grip, check...
Sight alignment and sight picture, check...
breathing, check...
Take up slack and slowly squeezed straight back...
Follow through...
I was having a bear of a time doing 25M bull shooting with a beretta 92F (blah!), as that style of shooting is NOT my forte lol!! What helped drag my scores up out of the gutter was focused dry fire.
Dry fire five times, than fire one round. Rinse and repeat. Train your mind as well as your body, concentrate and focus. Use your dry fire to get you into the mental "zone".
If you have a training partner, incorporate dry fire with a dummy magazine drill. Dry fire 5 times, than have your partner load a magazine in your weapon that may or may not have a round in it, aim at your target, go through your sequence and fire. If you flinch even though there was no round in the mag, take a break, refocus, and dry fire again. Concentrate and dry fire until you can fire without flinching when your partner gives you an empty mag, and your round lands where it should when he gives you a loaded mag.
Look at the targetry you are using.
Do grouping drills using the smallest possible target size. I use black bullet pasties on white paper, or white pasties on black out to 10 meters, and adjust accordingly as distance is increased. Smaller targets require finer aiming, and a more disciplined application of the fundamentals. The smaller the target, the tighter the group.
Another option is to use a lighter load. If you reload, load some light weight rounds with low charges to train with, than work up to heavier rounds with a higher charge.
Don't get frustrated. Handguns are very sensitive to fundamental errors we make, and they require consistant training, but you can do it!