Quoting Sadie: So in ♥:" Seems werid you would have to wait till 6 weeks i wonder if they would still give it to you or make you come back? I told them my lmp was may 15 and it was actually jun4..."
They had my friend schedule another appointment and come back when she was 6 weeks. They performed another ultrasound to make sure dating was correct, and then gave it to her. I guess before 6 weeks it's hard to say how far along you are since there isn't much to see? That would be my best guess though.