Is this normal?

Mekaiela

So would this change my due date? I had ultrasound today and according to doctor I am measuring 4 weeks 2-3 days but according to when I ovulated I should be a week further. And missed period puts me at 5 weeks 3 days. Does this change my due date?? Or does this mean the baby is just smaller or not growing? So nervous for my little miracle rainbow bean.