It's actually in the name. You are a resource for a purchasing department. I can't understand how people come to assume HR is on their side: it's not a union.
BTW all of what you described is not unique to women. I have at least few friends that don't negotiate, don't seek alternative offers and because of that are disadvantaged when it comes to earnings. Periodic pay rise is just a device to dissuade employees from seeking their market value and appropriate compensation. The main reason for its existence is to profit from what happened to you.