Usually I would have my period by now, as lately my cycles have shown I O on CD 17 and my period will start up 12 dats later. Today I am officially 14 DPO and no sign of period as yet. This is really odd. Yet I can't be pregnant as we always use condoms. Can being on antibiotics delay O? Maybe I Oed a day later than I thought? I don't know. Just when you think you have a consistent pattern going on it all goes and chsnges.