The normal menstrual period is three to seven days. There are several reasons why your period has been clean for several days and has come again. First, ovulatory bleeding may have occurred, resulting in a small amount of vaginal bleeding. Secondly, it may be caused by the presence of serious cervical erosion or cervical polyps, which may lead to the rupture of local blood vessels, or by the presence of malignant changes in the cervix. Third, if there is adenomyosis, submucosal fibroids, etc., which affect the contraction of the uterus or hormone secretion disorder, it may also lead to menstruation after menstruation. Fourthly, it may be related to the withdrawal bleeding of the endometrium caused by taking contraceptive pills. When a woman has a clean period for a few days and has a period again, it is best to go to the hospital to do gynecological ultrasound and physical examination for a detailed examination, according to the different causes of the treatment and its effect is better.