metformin delayed ovulation?

So this is my first month on metformin. So far I've had hardly any side effects, so thankful for that. I ovulate regularly and have fairly regular cycles so I am right around the time I should be ovulating right now but I am using the clear blue digital opk and I'm still getting the blank circle when normally it would be either blinking smiley by now or the solid smiley. Have anyone had delayed ovulation while taking metformin?