Knowledge needed

I had a blood test done at my doctor and then another follow up to see if my levels were rising and the doctor said they were beautiful. My last period was 3/28, so she said she's putting me at 5wks 5days. I got an ultrasound done somewhere else by just a tech and she did the transvaginal scan. She assessed it and told me I was 4wks 5 days. I'm a little confused because at this point in time, a week is a big deal!! I've been feeling fine and haven't had any bleeding. I'm scared! Has anyone had something similar happen?​