Hi Lolly,

With the pill i was taking, and most pills, you have a 12 hour period around the usual time you take the tablet. ei.. i take my tablets at night before i go to bed and one night i forgot to and took it the next morning, but it was within my 12 hour period of my usual time to take the tablet. That is the only thing we can put it down to.
Though, i also dont think the brand of pill i was taking was all that great as previously when using other brands my period would come on a Tuesday without fail through a 28 day cycle and since i switched to that one my period would jump between the prior sunday and the regular tuesday.

I cant recall being sick or having diahorrea that month at all, so it was either that day i missed my regular time or a dodgy pill...