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The cause for delayed periods can be hormonal
problem and even pregnancy
if you are sexually active.So if you are pregnant or you have any other disease or problem the periods may not come easily.You have already used Medroxyprogesterone
so you should get periods with in a week of taking the tablets for 5 days.Now i would suggest you to get a pregnancy test done if you are sexually active and if you are not sexually active then you need to consult a Gynaecologist and get investigated and she will treat you as required.