Hello, and I hope I can help you today. It is true that you can delay your menstrual cycle safely by taking progesterone. Unfortunately, it can make your cycle irregular in subsequent months until your body gets back to normal again. In addition, progesterone will make your period lighter in the first few months following your treatment, which is why progesterone is also used as a treatment for heavy periods. It thins your uterine lining, which means less blood and tissue build up over the month to be shed at menstruation. However, if you and your husband have been having unprotected sex, pregnancy can be a possibility as well. So if you never had real bleeding like a period in the month after you finished the progesterone, you should perform a urine pregnancy test as well. So these are a few possible reasons why your first cycle off progesterone was abnormal for you. If you are not pregnant, I am sure your cycle will go back to normal with your next cycle. I hope I was able to answer your question today and that this information was reassuring. Best wishes, Dr. Brown