Are these due dates even right?

Brandy
I know expected due dates are estimates because the baby can come at anytime but I'm wondering if an average pregnancy lasts anywhere from 38-40 weeks, if I'm just counting from the day i conceived I'm at 36 instead of 38 weeks and 38 if I'm counting from my last period. To me this sounds devastating. It sounds like I'm at 36 weeks. I don't know maybe I'm having a dumb pregnancy brain moment. It just seems like on average most women have their babies at 38-39 weeks and I feel like I'm behind but according to the scans I'm measuring on time but I'm not even dialating. Right now I'm 38