How can a woman know if she is fertile or when she ovulates?

Basal body temp, OPK: There are multiple ways to know whether or not you ovulate . The cheapest way is the basal body temperature where you take your temperature every single morning when you wake up and look for a rise in temperature midmonth or mid cycle; that's caused by ovulation. Alternatively , you could try ovulation predictor kits or testing day 21 progesterone.

Body temp!: Ultrasound can demonstrate ovulation occurring, and temperature changes in a women can also tell you when ovulation occurs. Many women will have a brief sharp pain during ovulation called mittelschmerz, a german word for ovarian pain during ovulation.