If you are getting paid for 80 hours twice a month , yes they are cheating you out of pay. If you are being paid by the hour I can not understand why they don't pay you every two weeks. Then you would get 3 checks several times a year. I would speak with your payroll person and have her/him explain it to you. If you have been cheated, most states have a dept of labor or some other agency that can help you recoup the wages you did not get paid.
Good Luck