Concerned first time mom

So, I had my first dr appt today. Thought I was about 9 weeks, turns out I am only 6w 3d. Anyway, they couldn't find any heart tones/beat. It's got me a little concerned seeing as a lot of women have heard theirs during the same time frame. I'm wondering if anyone has any advice/knowledge/positivity they'd like to share with me. It would be greatly appreciated. Thank you