Need your help ladies!

I’ve never ovulated on my own as far as I know. Been through 3 rounds of Clomid and now on my first round of Femara. For the first time ever I have had ovary pain on and off for a couple of days. Is this a sign of ovulation? If so, how far ahead of actual ovulation do you feel the pain? (I go to the dr in a couple of days for ultrasound to make sure I have mature eggs). Doing opk’s but no positive yet. Currently on CD 12.