My period goes this way December 31st, February non, March 1st, april 2nd, may 26th, June 20th, July 21st. How can I know my ovulating period.

Your periods are. Between 25 to 29 days. You add the total #of days the divide by the # of months. You then get the average cycle length, Once yo have that, subtract 14! and you have the day when ovulation is most likely to take place, GOOd LUCK.