ultrasound dating

Allison • Mommy to 3 angels 5/1/16, 12/14/16, 7/13/19 and Jonah 🐳🌈2/8/18
I read on the American pregnancy website that ultrasound can be off 5-7 days in early pregnancy and my doctor confirmed this so when I measure off by 7 days she wasn't worried anyone deal with this? It has me so stressed out