I'm using clearblue OPKs this cycle, not the dual hormone ones, these are the ones that come up with a circle or static smiley face if you are due to ov soon. I wondered though, I've heard of others using several OPKs a day, just to.catch the peak, like one in the morning and again in the evening, with the clearblue OPKs it says to.only do it once daily. If I were to do it Am and it was negative, could you, in theory miss the peak, if you ov'd later pm? Or would the opk come up with a smiley face still, am, even if you were going to ov pm time. Sorry if that's confusing! :)