Mine's also been weird - on day 6 of the whole30 my period started out of the blue with zero cramping and a few days early. I'm now on whole30 day 22/CD16 and again it showed up out of the blue this afternoon! Noooo! No cramping which is awesome, but no no no to a 16 day cycle, yikes! I'm not on any BC and have been having shortish cycles, but nothing like this!