So my period is irregular , it’s on a 42 day cycle . My last period was March 14th so it wasn’t based off my last period it was based off fetus size at the time of my appointment which was May 7th and my OB said I was roughly 4& half weeks maybe 5.

Based off an app i ovulated April 11-18th.

When my doctor did the circle calculation he said I’m due Jan 2,2021.

I had sex April 11th, and April 18th.

How could I conceived on the 11th?? I’m confused I thought conceived means when sperm meets egg.

*Someone educate me. I’ve never really tracked ovulating .

Ps: I only slept with one person I just would like some insights and knowledge