Measuring 2 weeks early

Hello I had an ultrasound on Tuesday (7/13/2021) and the ultrasound tech said I am measuring 2 weeks early

She asked when my last period was (5/18) and inputed it in her machine and said I should be 8 weeks.

I have normal cycles that are usually around 28/29 days.

I got worried when she said the baby is not measuring 8 weeks but it is measuring 6 weeks

She did find a yolk sac

I am wondering if anyone has a similar story and would share what happened

Thank you so much