Baby measuring a week ahead

I had an ultrasound today and the ultrasound tech told me he is measuring a week ahead. In previous ultrasounds he always measured a couple days ahead but now it's a whole week. Should my due date change? The ultrasound tech said my due date comes out at June 19th instead of the 25th just based on his size. Also should I worry if he's measuring a week ahead? Or is it somewhat normal?