do you have a decent fps and ping?
also tell us what mouse and pad you got, also your ingame sensivity and dpi.
finding the sens that works for you can help alot, also make sure you have a big soft mouse pad and a mouse and fits in your hand perfectly and is comfortable doesnt lag
once you find your perfect combination you can aim real smooth, my aiming became unbelievable better when i got a big pad and a gaming mouse and lowered my sense, this way i can be really accurate in matter of millimeters.
try not to push yourself too much with a single gun, im not that good with shotguns so i dont spend weeks trying to be goodwith shotguns and endup taking 10 chill pills a day-_- (this a true story, i got so mad i couldnt use sg that i had to take a valium before playing ! dont try at home!) im good with rifles so i stick with them mostly but also try to stay flexible, different situations and locations require different guns.
so story short, find out what really is holding you back, get a decent gaming gear, find the perfect sense( you can keep it flexible, low sense for sniper, mid sense for rifle etc..) and practice
hope i could be usefull, hope you become a pro soon enjoy.
p: i might have multipe gramatic and typing errors, im aware, dont be toxic and throw at in my face cruelly, jsut whisper in my ears gently