Why is it that you believe you are not ovulating? If you are charting your basal body temperature (bbt) and this shows no clear, sustained temperature rise, then it is likely you did not ovulate for that cycle.
If you have only recently started charting your bbt, and notice an anovulatory cycle, bear in mind that most women will experience the ocassional anovulatory cycle, so one anov cycle does not necessarily mean you are not ovulating regularly. If you have consistent anov cycles, you should see your doctor as there are many ways to increase your chances of ovulating both naturally and with medication.
If you do not currently chart your bbt (i suggest you do as this is an invaluable ttc tool!) there are other signs that indicate you are ovulating such as fertile cervical mucus (the consistency of raw egg whites) approximately 14 days before the start of your next period and a high, soft cervix. Some women also experience ovulation pains around the time of ovulation. You can also purchase ovulation predictor kits fairly readily that indicate a surge in lutenising hormone (lh) which precedes ovulation.
The most reliable way to determine ovulation is by charting your bbt. They also have huge amounts of info on fertility and ovulation as well as charting.
If you are not ovulating, it may be to a hormonal imbalance or a vitamin/mineral deficiency. Best to contact your doctor who will be able to tell you for sure and also provide treatment to ensure you ovulate again.
Good luck!!!
Fiona