On a 28 day bc cycle, what do would be the potential ovulation day if the bc happened to not work?

I'm on ortho tri-cyclen (not low, the higher dose one). It has a 28 day cycle.
Would I go by when my period stops, or the first day of the hormone pills (not the week of blanks)?
Thx.On a 28 day bc cycle, what do would be the potential ovulation day if the bc happened to not work?
Every woman ovulates at different times, some even ovulate when they are menstruating. However, the "average" ovulation day for a "perfect" cycle is 13-15 days.
1st day ur period started, day 14 is ovulation day but 3 days b4 and after it is possible to get pregnant
your new cycle starts on the day u start bleeding. so on your first day of bleeding count 14 days and that gives u a approx.
so 14-21 days u are able to get pregnant.but if your even 10 pounds over wieght the pill decreases in it effevtiveness and it does the same with sokin aswell. so u have a higher risk of getting pregnant as well.