Your periods can become irregular when you come off of birth control. I believe that should count as your last menstrual cycle. When you start to have a period that is the start of a new cycle. Try tracking your periods by charting for the next couple of months (there are some ovulation charts on line), that should give you some idea of when you should ovulate by checking for your fertile signs.

The Billings Ovulation Method
The Billings Ovulation Method (BOM) is a means of natural fertility regulation.
The BOM is based entirely on the symptoms of fertility and infertility observable at the vulva.
It does not use any form of rhythm counting, temperature taking, drugs or devices.
There are four simple rules of the Billings Ovulation Method which are applied whether the
couple wishes to achieve or avoid pregnancy.
Three rules (the Early Day Rules) apply to the time up to ovulation, when the peak day of
fertility is identified. The fourth rule (the Peak Rule) applies once the Peak Day has been
recognised.
The BOM is applicable from menarche to menopause, in times of breastfeeding, post
hormonal medication and when irregular cycles occur. It is applicable to achieving or
avoiding pregnancy. The BOM has proven helpful to couples of low fertility in achieving
pregnancy and should be the first resort in cases of apparent infertility.
The use of the Billings Ovulation Method is not compatible with barrier or hormonal
forms of contraception, either during the learning period or for family planning
purposes .
Hormonal medication such as that contained in the Pill and fertility control implants regulate
the hormone levels and interfere with the functioning of the cervix, thus distorting the natural
symptoms of fertility. It may take some time after ceasing this type of medication for the
natural symptoms of fertlity to recover.

1 Facts About Fertility
Ovulation (the release of one or more eggs from an ovary) occurs within a 24 hour period
and only once during a menstrual cycle.
Day 1 of menstrual bleeding is the first day of the cycle.
The time interval from day 1 to ovulation may vary.
The time interval from ovulation until menstruation is about 2 weeks.
Ovulation will occur early in a short cycle and later in a long cycle.
Observing the cervical mucus symptom gives information about being potentially fertile or
infertile on a day by day basis.
The fertility and infertility patterns ahead of ovulation vary from woman to woman.
Once released from the ovary, the ovum (egg) lives for 12-24 hours, unless fertilised.
Sperm cells need suitable cervical mucus to survive and reach the ovum in the Fallopian
tube.
Sperm cells may live for 3-5 days in suitable cervical mucus. At infertile times they will
survive in the vagina for only an hour or two.
Ovulation sometimes occurs before bleeding ends

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