Professional opinion needed for Accounts Payable/Receivable?

I work at a car dealer where I started as the evening receptionist making $7.50 an hour. I was promoted after 6 months (after giving my 2 weeks notice*) to daytime receptionist and compensated with a raise ($10.50). After a full year I was moved into our accounting office and was made the accounts receivable and payable clerk and my comptroller gave me a $0.50 raise. I'm also a backup when needed for our receptionists whenever one quits, needs a day off etc. I train any new receptionist we have to hire and I've also learned how to do more tasks in our accounting office (dealer trades, putting contracts together for deals, warranty credit postings etc.). I've been here for a little over two years and I'm still finding it hard to get by with the money I make. I want to ask for a raise but I'm not sure if I'm in the position to. I've researched what people are making on average at my position and its more than my current rate. Should I wait to ask for a raise or should I just go for it?