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Ovulation usually returns in a month or two after stopping birth control pills making you fertile. However unprotected sexual intercourse during midcycle is more fruitful than days before expected date of period and after period.
As per your details, it is unlikely that you could be pregnant now. The delayed period could be related to hormone disturbances or some infection.
I understand your concern. I suggest you to have more unprotected sexual intercourse with your partner on the days of ovulation which is during mid menstrual cycle. And do not forget to use folic acid
All the best.