Hi, me and my gf have sex every month or after 45 days after her period over. She miss her period 2-3 days every month. Her last period was on 21 dec and after tht her expecting period date was on 21jan but it doesn't work for her it happen on 30th jan (9-10 day delay) what's the problem? Plzz answer me. It happen due to sex or another problem? Thanks