Thank you for your reply.
If you are being paid under the table and not paying taxes, both you and your employer are violating the law. Your employer is violating the law by not paying payroll
tax, making quarterly withholdings, and providing you with proper paystubs. However, you are also breaking the law by earning money but not declaring your earnings as income. The problem is that when you report your employer for paying you under the table, you are essentially also reporting yourself. Your employer will be fined, but you inevitably get an angry letter from the IRS demanding unpaid taxes.
This makes situations where an employee is paid under the table very difficult. I am quite sympathetic to employees in this circumstance, as they are almost always being taken advantage of, but the reality is that they are between a rock and a hard place.
Now as far as workers compensation insurance goes, if your employer is not in the construction industry and does not have more than 4 employees, they don't need to have workers comp coverage anyway. But if they do have more than 4 employees or are in construction then they likely must be covered. You may encounter an issue in "proving" they have more than four employees if they are paying everyone under the table, but assuming you can get past this hurdle, it might still be possible to get compensated through the uninsured employers fund. You would need to contact a workers compensation attorney for more information about that.
I wish there were better options for you, but I am trying to be honest about the legal reality of your situation. It may just be that your best remedy is to find another job that's "above board," so to speak," and to move on. I hope that you find this information helpful. Please do not hesitate
to let me know if you have any questions or concerns regarding the above and I will be more than happy to assist you further.