There are many reasons for not having a period for more than three months, if you have had sex in the last three months without contraception, there is a possibility of pregnancy, you can use test strips or come to the hospital to draw blood to determine pregnancy. If you find an unwanted pregnancy, you can choose abortion or medication to terminate the pregnancy. If you completely rule out pregnancy, it may be caused by abnormal ovulation in the last three months or endocrine disorders such as polycystic ovary syndrome. In addition, if you have lost weight in the last three months or strenuous exercise, as well as mental trauma, may also affect the endocrine axis of the ovaries, so it will affect the ovulation, thus leading to menstruation can not come on schedule. In this case, it is recommended to do ultrasound examination to see the condition of the uterine adnexa, and if necessary, take progesterone to promote menstruation, intramuscular injection of progesterone is also possible, usually injected with forty milligrams a day for five consecutive days.