How will i know my fertility period if im irregular in period?

Difficult: It depends on how irregular you are. If you periods comes 2-3 times per year you may never be ovulating. If it comes between 30-45 days, ovulation kits can help. Taking your morning temperature can help but usually is a pain in the neck and does not show too much. Certainly an ultrasound and bloodwork an also help figure out when you are producing an egg and ovulating.

Difficult: It's very hard to predict ovulation when the menstrual cycle is irregular. Sometimes with ultrasound or with ovulation predictor kits the timing can be guessed. Usually ovulation occurs a majority of time 14 days prior to menstruation.