Ultrasound already?

I had my last period on sept 28 and after ttc for an year I got my first BFP thank God last Friday the first time I tested on this cycle. Both on a first response and on a clear blue digital. I went today to my doctor and she did me an US, she was able to see a "bag" on the uterus and nothing else. I don't know exactly when I ovulated but normally it's after CD20. Now I'm kind of freaking out! Is it ok that the doc didn't see anything else? Is it just to early? She told me to come back on two weeks time... just looking for some support. 

Xxx