Hello! I have such a question. How often does ultrasound error? The ul…

Hello! I have such a question. How often does ultrasound error? The ultrasound was scheduled for February 24th to February 27th. But according to my calculations, the deadline is March 2nd. If we believe in ultrasound, I am pregnant for 40 weeks and 4 days. But the birth is still not thinking about starting. Although the belly has dropped slightly (heartburn stopped bothering me). But contractions are still nowhere near coming. What should I do?