Why are my periods different every month?
As your body gets used to your menstrual cycle, your period may be irregular. It is important to remember that everyone’s body is different and there is no norm as to when your period should come. Birth control, pregnancy, and even menopause can all affect the timing of your cycle. It's always a good idea to check in with a doctor if you have concerns.
"A period that comes every cycle at exactly the same time is not the norm. Of course, cycles are irregular when they're first starting, as they're coming to an end, and around the times of pregnancy and changes to contraceptive methods. But even outside of those times, slight variations in timing and symptoms are common." It's always a good idea to check in with a doctor if you have concerns.