Hi, Thanks for the query. I understand your concern. I understand that you started taking Norethindrone in mid cycle & so skipped your period in September..stopped your pills ,had sex in couple of days...&are afraid of falling pregnant due to possibility of ovulation... Please understand there is no ovulation when you are on oral contraceptive....so you do not have a chance to conceive with the sex after stopping the pills Actually you would get periods within a week of stopping the pills. In case you do not get periods in 7-8 days of stopping the pills.. it can be... -possible conception before starting the pills in August....Home pregnancy test would reveil it.&pregnancy needs to be terminated,as Norethindrone is notorious to cause foetal abnormality. -Hormonal imbalance causing irregular periods . Please consult a gynecologist for expert advise. Thanks.