Send yourself a registered letter - if it does not arrive - ask the post office. However, your real problem is far more complex and needs the immediate attention of an attorney as you could be facing serious criminal charges.
I believe that Jonathan Levy's suggestion about sending yourself registered mail is a good idea. However, it sounds like receiving your mail may be the least of your concerns at this point. Additionally, you should be careful about the details you provide in an open forum such as this one (i.e., Avvo). My suggestion is that you immediately contact an attorney to discuss your situation more fully.
I agree with my colleagues above.
You should also be aware that, even if you are getting your mail, the feds may be getting information from the mail you receive. They can get what is called a "mail cover" which gives them the information, if any, on the front and back of the mail you receive. Mail covers are sometimes used in an attempt to add a piece or two to the puzzle that is a complicated investigation.
Get counsel now. Better safe than sorry.