Accurate day to take an HPT?

Hi all. I had sex on the 14/15 of December and my boyfriend came inside of me. I’m on the pill, so I should be okay.. but I tend to be a worry wart so I just want to take a test to ease my mind.

I’m currently on my placebo week and my period has not come yet, so I was wondering when would be the most accurate time to take a test? I will take two tests either way. My placebo week ends on Sunday if that means anything! Thanks :)