Sorry, I figured I might have made it confusing! ^^; I too use an app to track my periods and predict ovulation and it makes everything soooo much easier!
Anyway, check out this map: http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/MenstrualCycle2_en.svg/850px-MenstrualCycle2_en.svg.png
As shown, you have the follicular phase (Day 1 to 13), ovulation (Day 14), and the luteal phase (Day 15 to 28.)
Notice how estrogen naturally rises in the follicular phase and slightly drops right before ovulation. After ovulation, the estrogen levels continue to fall and the progesterone levels rise in the luteal phase.
This is what we're trying to imitate when it comes to cycling PM. You take PM
only in the follicular phase since estrogen naturally rises in that phase. In this chart, the day of ovulation is day 14 so ideally, PM would stop being taken around day 11 or 12. Still though, remember, everyone's body is different so don't follow this example chart strictly. It's just a general example chart. Your day of ovulation may come on a different day.
Even though I use an app, I don't depend too much on its predictions of ovulation because PM can alter your cycle a bit. So I depend on basal body temperature charting and studying my vaginal/cervical fluids. You'll know you're ovulating or near ovulation when your fluids turn from creamy to stringy and sticky like egg whites.
Also I actually use two brands of PM to make them last longer. I take one Thanyaporn pill a day when I'm menstruating since it's 300mg and is also a compound so other herbs are mixed in, and then switch to Ainterol and do their regular dosage when my period ends.
My side effect was not fun. -.- There is a chance if you take PM while menstruating, you may get nausea and stomach cramps. Some women experience that and I was one of the unlucky few. T__T Bleeeeech!! Although I did read a post saying that these went away after the second cycle because this member's body was now more used to the PM. I can't personally confirm this yet, but if I do my low dosage while menstruating and still get yucky cramps and nausea, then I'm going to start PM near the end of my period or simply wait until it finishes. If my body stays cool, then we're good. 8)