Suggest Remedy For Delay In Periods

Hi I got off depo Oct 2011 have had a normal period lasting 7 days since Oct 23 coming around the same time each month until now My cycle phase is at average 30 days. I am now 3days late i have took 6 HPT all negative what could be going on with my body No cramping or PMS signs nor pregancy. I was on depo 7 years but when i called the quits my body was normal up and til now. please explain