The best thing to do is to talk to an experienced employment attorney quickly. You should also document as much about what has happened as possible. Save emails and text messages, talk to witnesses and write out a diary of events. Your employer will likely dispute your account, and the evidence you have can help you prove what happened -- and what still may be happening. In some cases, you can also file reports to your HR department, the EEOC, or even OSHA for safety-related issues such as retaliation for refusal to do dangerous work.
What you may discover is that you are not at all alone. If the illegal activity has impacted you and your career, there are likely other employees who have found themselves in the same position. Getting their statements and accounts can help to establish a pattern of behavior. This is important if your employer tries to claim that what happened was a one-time event or a misinterpretation.