been playing call of duty alot poor aiming smh?

yesterday was by far the worst cod days I have had I train my aim quite often with the bots but when I get in pubs I get destroyed...and I hold my controller like a million ways trying to perfect my aim but idk what to do and kontrol freeks dont work for me.....any advice on thumb placement on the controller and thumb movement or something I just can't land the first show or stay on target smh