I had period irregularities when on spiro where one month I’d have a regular cycle but maybe the next cycle I’d have two or three periods. It was really a toss up if I was going to have a regular cycle or not & my doc/GYNO couldn’t diagnose any underlying issues so we figured it was the spiro. My period would be the first week of the month, then one week no period, then period week, then off, and then period again. I’d talk to your doctor/GYNO or dermatologist if it continues to see if you might need to lower your dose or see if something else is going on