Throughout the menstrual phase, which lasts about three to seven days, the body sheds the uterine lining if no pregnancy has transpired. This can be when menstruation occurs, and it may vary in flow and period from Individual to individual. Check your blood progesterone or PdG (urine metabolite of progesterone) https://eirmedltd.com/are-regular-periods-a-good-sign-of-fertility