Pregnancy question

Tamara • Mommy to my 2 beautiful baby boys, Nathan Louis💙 born August 12, 2017 and Parker Joseph May 6, 2019❤️ My whole world😍
Okay. So my first day of my last period was July 13. But I know I conceived or week or more later. Does that mean I still count my first day of my last period? Just curious because I know I conceived after my first day. Curious if that's the same as they tell you when you go to your first appt.