SUPER SHORT ANSWER: You should start your period between 1-5 days.
Well...I don't have a vagina...so YOU should prooobably take this advice for what it is, speculation. That being said, just because I don't have a vagina doesn't mean that I haven't studied many of them. I've also had many girlfriends in the past who were on the pill...and every single one of them had a vagina.
So I know that you take the pill 3 weeks, then the 4th week is sugar pills. They do this so you stay in the habit and cycle(no pun intended) of taking the pill regularly, so week 4 every month your body goes off the pill and your body is allowed to have it's period.
The pill tricks your body into thinking it's already pregnant, I mean REALLY over generalizing here, but your body is like "semen in my vagina? ah heeell naw, I'm already preggers." and so there's no fertilization of your egg and the magic of science.
So some women skip over the 4th fake week and go right into the next pack of pills...thus they never have a period again. No one knows the long term effects of this, so don't do it without talking to your doctor, and I fucking Haaaate doctors...so if there were ever a time I'd suggest you consult these assholes, it would be on this issue...and anything relating to your reproductive health.
So...If you start taking the pill your body is thinking "what the fuck is going on here?" and it's not going to match up perfect where this day your starting your period, but maybe tomorrow your going to have a grumpy vagina...and boy have I dealt with a few of those...anyway...
I would say, take your pills like clockwork...but remember that your not a robot and your vagina is not an ipod. So it needs to adjust, it's like when you start a diet and you hate healthy food, but after 3 months you love it and fast food that you once loved...noooow makes you vomit and poop all over the place at the same time. You body can adapt and change drastically. Next month, when you go off of your 3rd week, I would expect a period...I mean if not randomly before then.
But let month one go by and by month two ask your doctor...without assuming anything bad. Once your body get re-calibrated, so to speak, you should end up just like how you were before going on the pill...regular periods...but now through the miracles of modern medicine, completely "immune" to pregnancy.
Anway, as always apologies for the overly worded answer. Hopefully you learned something new, or if nothing else found something I said funny or amusing in some way. In the end I am really hoping that after reading this, you know more than you did before and feel a little less worried about it and that my "advice" was in someway useful to you.
