help! employer not pay full

I was hired by a consulting company, and they told me they will pay me biweekly, but I got my first check after 2 month, and the second check after another 2 month. The bad thing is, I have 3 weeks not get paid. I called them, they didn't answer my question. Anyone know if I need a lawyer to talk with them? How much will cost? I'm so mad with this company. I don't want fire this company is because the work I got is what I like and have a good pay rate. how to solve the problem? anyone can give me some suggestion? Thanks!