Hello,
If you have a consistent 28-day cycle, ovulation is likely to begin about 14 days after the day your last period began and this is when you may become pregnant. It is doubtful you would become pregnant on the 24th day of your cycle.
If your cycles are somewhat irregular, subtract 18 from the number of days in your shortest cycle. When your next period begins, count ahead this many days. This is a reasonable guess for your most fertile days.
__________________
