I think you could approach your boss and ask when is a convenient time to talk to him/her.

You could say something like- " I am a little worried that my hours have been reduced to half of what I've been doing over the last 2 years. I've also noticed that some people who started here much later than me have been getting more hours. Can you tell me the reason for that? If you have any issues with my performance I would like to know about it so that we can have a discussion about it. I just want to let you know that I am available for and, very keen, to work more hours."

This kind of language is conciliatory and not aggressive and hopefully will open the door for courteous discussion.

Why don't you try your luck with another or get another part-time job.

If you got talents you can be hired as soon as possible. You can work for a full time, part time or even as a freelancer.

http://www.hireonlinetalent.com/

Whats interesting is that you can be hired anywhere you are in the world.

Am sure this will suit you because I am hired from this as well.

To be honest there is a new manager cuz they need to save money so anyone who been working there the longest and makes the most money will have their hours cut no exception. The new people getting more hours are the people with the less paid. Now you have to talk to the manager and kiss that person butts so you can a least get enough hours. You have to show the manager that you are a hard worker too, like going up to the manager after you finished a assigned job and say is there anything you want me to do Mr. or Miss manager, I'm always available if you need help with anything or everything. Just show the manager that you will be there anytime to work and you will be the person the manager can be depend on. Make sure to tell the manager that you been with the company longer and you know the ropes of the business. Remember to always speak up and don't trail behind cuz you will lose.