You sure your sensitivity is correct? Those are just for fine adjustment, but can easily be played without. More of a feel thing, I tried them and hated them.
Start a private lobby with bots and run around with a gun you like, use it at whatever range it should be used (SMG - short to medium, Rifle - med to long in most cases) and see what causes you to not land your shots (on bots you should be hitting almost every bullet). Do you sweep from left to right/right to left past before correcting back? Sens is too high. IF you play mostly SMG, run a higher sens, like 6-8, if mostly rifles, like 4-6. But then again it is all feel. I would try changing just your vertical sensitivity alone (but think you just need to play more to get used to it), but if you are accidentally moving it up and down, could be you arent comfortable with the controller yet in faster paced FPS settings.