It depends on your cycle. A typical cycle is 28 days long. Therefore it should be 28 days after the day you started your last period. But there are different cycles. If this is a reoccurring issue being on birth control will help manage your period better. Thats what I did.
First date of my last period was 18/02/2010
My last period was on the 2 jan 10 when am I do again.
Tomorrow
My period hasn't come yet and today is march 28 and yeah maybe later it might come but if not ..I'm pregnant