What Causes Delayed Periods After Taking Meprate While Having PCOD?

I have irregular periods and has been diagnosed PCOD. My doctor prescribed me Meprate (Medroxprogesterone acetate tablets) 10 mg for 5 days, 2 tablets a day. she told me to take the tablets and that i should get my periods after 2-3 days. It has been almost 8 days now since i finished taking the tablets but i did not get my periods.