OPK Question

Allisyn
Haven't used OPK's in years. Decided to give it a go this cycle using CB advanced digital. Started a few days after my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> said my fertile week started. 
Last period was 10/7. I average a 28-31 day cycle. <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Period tracker</a> says 30 days is my "average." Fertile window started on CD12, according to the app, and ends on CD18 which is tomorrow. App says today should be O day. We've bd'd CD 11, 12, 16, 17 and plan to tomorrow and Tuesday. 
My first test with the digital was Thursday, CD14. Flashing smiley meaning high fertility and a rise in estrogen. I haven't gotten the solid smiley which indicates the LH surge, just a bunch of flashing smilies. Today I decided to grab a pack of store brand OPK's and took three of them throughout the day, all obviously negative. 
Wondering if it's possible that I started the OPK's too late and might have missed my surge but I'm getting the flashing smilies because my estrogen is still elevated & that's what the flashing smiley indicates? Or is it possible that I ovulate later in my cycle? I've had varying amounts of EWCM all week, and sore nipples. 
I'm driving myself looney over here with the confusion. I suppose if this month were a short 28 day cycle, I missed the surge by testing too late. 
Any insight would be awesome! Thanks!!!