Knowing exactly when you ovulate, helps you know your exact DPO days. Taking opk's and BBT have helped me understand my cycle perfectly! Believe it or not, taking the OPKs and bbt made TTC a lot less stressful because I knew exactly when I ovulated, and knew my exact dpo day. So if the pregnancy test was negative, then I'm not pregnant, and I try again without stressing over thinking I'm late and not getting positives. I have irregular cycles. This last cycle was 38 days. I ovulated on January 18th and I did finally concieve! Also, I'm technically 4 days late, getting very strong positives and still getting negative OPKs.