So, I've been using OPKs for about a year now. One thing I've noticed is that all brands say to stop testing once you get a positive but I wasn't getting temp rises until like a week later so the positives never added up. My fertility doctor told me to keep testing with OPKs even after a positive and low and behold we figured out that I had delayed ovulation 5 out of 12 cycles. Meaning my body would get the LH surge and fail to release an egg and try again 4-7 days later. This month I had a positive OPK on CD 15 and went negative  the next 4 days and then I had another surge on CD 20 and got a temp rise on CD 21. We have missed the egg a lot of cycles because of this. If I didn't keep testing and temping I would have never caught the egg. Just wanted to share my experience since my fertility doctor said that failed ovulation is common, and that your body will surge again and hopefully release an egg with the second LH surge. One month I surged 3 times and finally ovulated on CD 25 verified by a thermal shift. I'm still in my TWW but I'm optimistic considering we have been inseminating too early because my body would gear up to ovulate and not actually happen till a few days later.