Last menstrual period vs conception date

I’m currently 7weeks+1- if I go by the date of my LMP. However if I go by the date of when I ovulated (which is roughly when I conceived- give or take a few days) I’m only 5weeks+1) Does this mean at my ultrasound on Sunday my baby could be measuring at 5weeks+1?? I’m worried that they aren’t going to be able to see anything? Thanks for you help in advance!