Measuring 8 days small...

I went in for my first US yesterday at 7w2d. That's according to my LMP but also, my fiancé lives 700 miles away, and the day I saw him coincides with 7w2d. My ultrasound tech was super rude though, and when she measured the baby at 6w1d, she chalked it up to me ovulating and having sex later. She didn't care that I didn't see my fiancé again for 2 weeks, so that's not really possible. I know they say within a week is fine, but I'm worried. The heartbeat was strong at 120, though I didn't get to hear it. :( Is it ok that he's small? She didn't seem at all concerned, just changed my dates.