The fact that the endometrium has reached 15mm and you have not had your period indicates that there is currently a thickening of the endometrium. There are many reasons that cause endometrium of 15mm and still no menstruation: i. If there is intercourse during ovulation, there may be pregnancy. Second, it may be caused by endometrial hyperplasia, which mainly includes simple hyperplasia of the endometrium, generally due to irregularity in its own work and rest schedule, resulting in disruption of hormone levels in the body. Third, see organic lesions, due to polycystic ovaries or ovarian tumors resulting in atypical hyperplasia of the endometrium, if it is thicker, you can do a diagnostic scraping. For postmenopausal women with endometrial thickening of 15mm, it is recommended to go to the hospital in time to exclude endometrial cancer.