Is there anything I can do about this? Work related!?

I've been working at my job for almost 5 years as a bagger and have not been promoted. I have seen so many people come and go it's pathetic. I've also seen so many people that have been there for far less time than I have been and get promoted. Now there is an opportunity for a job that I really want and it's in Liquor.... but here we go again someone that has been at my work less than I have been is going to get the job. He's a guy and I think that's why he got the job. Or maybe I'm just a push over. I don't know but it's so wrong. I work so hard. I never do anything wrong, and I'm a good worker. I'm very rarely late. I also work in a union. Is there anything I can do about this? or the union can do about this? should I give them a call?