Crazy Post Ovulation Temps! Help!

*S*E*C*O

Hi Team! This is the first month my husband and I have tried to time unprotected sex to receiving a peak OPK. Of course this is also the first month my temps have not reliably risen following ovulation. What gives?! Does anyone have any advice or thoughts as to why this might be?

P.S. the first part of my cycle is unreliable because I was lazy about taking temps on time. I received an unambiguously positive OPK on CD 13, and this chart (Femometer) and my fertility friend chart show ovulation on day 14.