Frustrating and confused

Been trying for a few months now.

Ovulation tests were positive this last time and we BD almost everyday during my “fertile” window.

<a href="https://play.google.com/store/apps/details?id=com.glow.android">Glow app</a> is now telling me AF is 2 days late, took a test and it was negative. No signs or feelings of AF coming.

This is CD 31. My average is about 30 and usually lasts 4 days.

Thoughts? Advice? I do take synthroid for my thyroid but the last two bloodwork tests I have had said my levels were all good and where they needed to be.

Am I not using ovulation tests enough? Not BD enough? Should I try switching up my diet or taking something to boost fertility?