I'm feeling moody on my girlfriend's birthday
Why are you moody on her birthday?
I'm pissed because I have done nothing for her birthday.
I think it is pretty rude to ruin someone's birthday by having a bad attitude. Just because you haven't done anything for her birthday doesn't mean you need to make her feel bad.
Look don't tell me what I should and shouldn't do. It's my girlfriend not your cheating wife.
I don't have a wife to speak of, so it is inappropriate of you to make claims like that.  Regardless of how you feel today, it is wrong to lash out, even at strangers, in that fashion.  If you treat your girlfriend that way, she might lose her patience and break up with you.