Due date off

So I went in for my confirmation appointment with my OB she did a pap and Transvaginal and this is what we saw. I was so happy but she was saying she thinks it looks like 4 1/2-5 1/2 weeks my last cycle started 12/27 which means I should be 7 weeks. She didn't seemed concerned but I can't help but feel confused. She said we would get a due date at our next appointment in a month.