I was with my ex boyfriend from June - no later then sept 12. I don't remember  the last time we had sex but I know no later then sept 12. I got back with my ex husband on sept 15. I am not pregnant and confuse about who the father is. My cycle is 30 day length and stays on 5 days, and I do have or had pcos. I just really need to know when I ovulated. My baby at 9 week scan was measuring 2 days ahead and at 3 scan she was within her week 25W1D - 25W5D from different measurement. Well is it to close to tell? Could it be ex boyfriend or ex husband?