it sometimes takes a while for your body to get back on track after taking the pill. it usually takes a few months for AF to come. lots of women on here use Fertility Friend charting website in which you take your temp every morning which will help you pinpoint ovulation. Ovulation Calendar and Ovulation Chart - Fertility Charting (its free).
best of luck.
come and join us in the TTC 1-6months thread. look forward to seeing you in there