Ovulation pains

How do you know if your ovulation pains are happening before, during, or after you ovulate? I feel some mild cramping, but my ovulation tests were a little screwy this month. It went from low fertility to peak fertility (completely skipping the high fertility step, but looked like it smeared so not sure if it's accurate this time around). I usually ovulate CD 16, I'm CD 12 at the moment. I wasn't expecting to ovulate yet, and I didn't have sex as much as I should have... I really don't want to be out this month.