That depends on the terms and conditions of your employment contract. Do you have one? What does it say about paying back bonuses or relo money? What promises did the employer make you as part of that written agreement.
You can sue for actual damages (if they are calculable) but punitive damages is just not going to happen. Further, I agree with Bubba Jimmy that you'll need a barrel full of money to give to a lawyer to handle this for you. It's not something that any lawyer is going to do on contingency. Call around if you think other wise.
Whether you are exempt or non-exempt is an entirely different issue and can be easily determined with a look at the US DOL website:
http://www.dol.gov/elaws/esa/flsa/screen75.asp
If you find out you are non-exempt you can file a complaint with the US DOL as well as your state's DOL.

