If you are ovulating regularly you should have regular monthly periods. Basal Body Temperature (BBT) with a special thermometer works, but the temperature only rises after you ovulate. Ovulation Predictor Kits (OPK) are more useful when trying to conceive as they go positive 24 to 36 hours before you ovulate, so you know your most fertile days. Drugstore brands should work; we recommend Ovuquick – search online and get the 9-stick pack not 6. If you have very irregular periods don’t do BBT or an OPK, see a Reproductive Endocrinology and Infertility (REI) specialist for testing to find out why you’re irregular.