I'm going to shout at my girlfriend
Why do you want to shout at your girlfriend?
She has been getting on my nerves lately.
Getting angry at times is normal for everyone. But you should try and avoid raising your voice as it can make things worse.
No need for all this naggy shit.
I'm not trying to nag you, I just want to to be aware that  screaming and yelling is very inappropriate especially with your girlfriend.