One of the expected side effects of birth control pills is a temporally lack of ovulation when coming off the pills. Normal ovulation is usually established after 6 months. Temporally lack of ovulations, however, can last up to 2 years. Without ovulation, menstrual cycles and periods are irregular. If you want to conceive you can take blood analyses for pituitary (FSH, LH and prolactin) and ovarian (estrogen and progesterone) hormones do establish if you are ovulating, or not. In this case, an ovarian ultrasound is also recommended in looking for ovulation. If the ovulations have not yet returned spontaneously, ovulation inductors (clomiphene) can be used to promote conception.