Hi & Welcome. I can understand your concern. Usually after taking Regesterone for 5 days you will get periods in a week s time. The possible causes for missed periods are: Poly cystic ovary disease, anemia, thyroid hormonal fluctuations, stress and strain,changes in diet and exercise which can affect the weight, recent illness etc. All these can influence the hormones which will regulate the menstrual cycle and can lead to menstrual irregularity. Sometimes the urine pregnancy test kits may not detect early pregnancy. So better to undergo ultrasound which will rule out the possibility of pregnancy and can also can find out the cause for the missed periods. If needed you can undergo blood tests for hemoglobin and thyroid hormonal levels. With the above tests possible cause can be find out and treatment can be given. When only hormonal problem is found, better to go for combined oral pills as progesterone pills didn t work. Hope the suggestions given would be useful.