Michigan gov didnt receive my 2006 taxes what should i do?

i may be freaking out over nothing but i mailed my taxes on 4-16-2007 .i keep calling the refund info hotline and it says they are working on returns received on 4--28-07 my return should have been received by now anyway it says there is no record of receiveing my return..if they really didnt receive my return what should i do??should i file again even though its past the time to file? any help on this matter would be greatly appreciated...