If your period is usually very regular, once a month, and you have normal sex, if you don’t have your period, first of all, consider whether you are pregnant or not, and you won’t have your period after you are pregnant. If the time of menstruation is more than 7 days without menstruation, or through the examination, there is no pregnancy, it is not normal, it may be caused by endocrine disorders, you need to go to the hospital for ultrasound and laboratory tests of sex hormone six and thyroid hormone, because endocrine disorders may lead to irregular menstruation. However, tiredness, late night, mental stress or obesity may cause irregular menstruation and delayed menstruation, so the cause should be clarified and treated.