I'm sorry to hear of the situation.
Your primary job does not appear to be a supervisory position---and I presume that you do not have a masters degree or a PhD either. So, that make the company's classification of you as a salaried exempt employee very possibly illegal. They can not simply call some exempt from overtime simply because they pay them a salary.
If I am correct in evaluating your situation, you may be able to collect overtime for all the hours that you have worked more than 40 in a week, dating back 3 years!
Additionally, if you can show that they employer deliberately misclassified you, you may seek liquidated damages as well. Liquidated damages is equal to the amount of back wages that they owe you and must be paid in addition
to the wages themselves---so you essentially get double overtime wages in the claim based on their willful failure to pay you. http://labor-employment-law.lawyers.com/wage-and-hour-law/Liquidated-Damages-and-FLSA-Claims.html
Here is an excellent article which deals with pursuing an FLSA claim---which you may do in either state court or federal court. Do take the time to review it: http://www.peterslawfirm.com/scottpeters/publications/trial%20aug%2008%20peters-walton-1.pdf
I urge you to meet with a local Employment Law attorney to discuss this matter. based on your suggestion that you work as much as 20 to 30 hours of overtime a week---even if you earn just $10.00 an hour, the money you may be entitled to could be as high as $75,000.00.
Here is a link which explains what it takes to be classifies as salaried exempt in the first place:
I hope you found my answer informative, even if the law is not necessarily in your favor. Please Accept my answer so that I may be compensated for assisting you. I wish you the best in 2012.