Sorry if there was any confusion with another expert jumping into the question. Apparently he did not see I was already helping you with this.
Tennessee protects employees who are discharged or terminated for refusing to participate in illegal activities or for speaking out about illegal activities. These claims are created under Tennessee common law and under a statute, the Tennessee Whistleblower Act, Tenn. Code § 50-1-304. See discussion in Guy v. Mut. of Omaha Ins. Co., 79 S.W.3d 528 (Tenn. 2002). Generally speaking, an employee must file such a claim with the appropriate court within one year of learning of the employer's decision to terminate employment. You may see the full TN statute here: http://www.peer.org/docs/tn/whistleblower_protection_law.pdf
Federal law has created other whistleblower claims, too. For example, the Sarbanes-Oxley Act of 2002 creates an administrative complaint procedure and a federal civil cause of action designed to protect the employees of publicly traded companies who lawfully provide information or otherwise assist in an investigation regarding any conduct which the employee believes constitutes a violation of federal mail, wire, bank, or securities fraud statutes, any rule or regulation of the Securities and Exchange Commission, or other provisions of federal law relating to fraud against shareholders. Sarbanes-Oxley prohibits publicly traded companies and their officers, employees, contractors, subcontractors and agents from discharging, demoting, suspending, threatening, harassing or in any other manner discriminating against an employee in the terms and conditions of employment because the employee engages in conduct protected by the Act.
It sounds to me as if you are afforded protections under both state and federal law. In would suggest you see a local labor/employment attorney ASAP in order to preserve your claim. You can find one here: www.martindale.com.
If you have any more questions, I will be happy to answer them. If you would like to accept my answer, make sure you do so in the top of my box so I can get credit for helping you. Thanks!