the past couple of months AF has been starting on the 9th then the 13th now this month today the 10th. how am i supposed to find out when my O day is if it keeps switching? i always started on the 9th now AF has decided to my a real pain in the butt because my DH and i are wanting to have a little one. i know to chart my temp but my i have been using the O calender. this month however idk what cyle day i need to put in?!?! 28? 29? 30? please help!! thanks!!