Ovulation

Its supposed to be the release of the female egg from the ovaries if i still remember my biology
Its supposed to be on day 14 for ladies with regular 28 day cycle.
For those with irregular cycle, its 14 days before menstration starts of a new cycle.

YEP, I agree with Coco29. Buy a book and read  . Also, you could get an ovulation monitor and follow the instructions on the pack 

Buy everywoman and read it, there are very many books on that topic, I know Ovulation runs for 3 days in a lay man term it is called unsafe period,I wont say your case is abnormal, it occurs between the 12th day and 15th day after menses. There are many factors that contribute to this may be you should see an expert, buy books and read them.

The day menstrual flow begins is 'Day One'. Circle this date on your calendar or chart and notate as 'Day One'. For each following month, circle Day One and continue this for for at least 7-8 months. Continue maintaining a record of the number of days in each cycle. When bleeding starts, circle the date on your calendar.

To determine the first day you are likely to ovulate, examine your records from previous months, find the shortest cycle, and subtract 18 from the total number of days in your cycle.

For example, if your shortest cycle is 28 days long, subtract 18 from 28, which leaves 10. Starting with the date you circled (Day One, the first day of your current cycle) count ahead ten days and draw an O (for 'ovulation') through that second date. This day will be the date you are most likely to become fertile - and frequency of intercourse should increase as the duration of this fertile period will extend approximately 5 days or more.