Ultrasound Measurements and Dates😑😵‍💫

So I went for my first scan today thinking I was measuring at 6w5d and it turns out I’m only 4w2d and baby is measuring at 5w2d has this happened to anyone else my first day of my last period was on the 9th of October🤔But my doctor seems to be happy with the scan and can see the baby🙏🏼

Should I go for a second opinion? Maybe I ovulated later than expected because I didn’t check for ovulation🙈

Am I stressing for nothing?