Sounds as if you are paid on performance, commission etc.
If so, then his customers spend more than yours do.
It's that simple and it has nothing to do with the fact that "you're a girl". Stop whining about body parts.
He spends a lot of his time doing nothing or socializing with coworkers talking on his phone. He texts during meetings (with the boss)
He’s been there only a few months longer than I. Prints out personal stuff on office printer shows up late leaves early.