A lot of people are afraid of asking for a raise at work, but when you think about it -- worst case your boss says no, best case your boss says yes!
However, you need to have a strong argument when you decide to make your move. Do some prep work and have your talking points ready to go. Know the salary range for your position, the value you add to the company and specific examples of your accomplishments at work. Consider timing too -- when you've been performing at the highest level is a good time to ask.