sonogram help

So went to the doctor. She did a sonogram and said its earlier than I thought-about 5 or maybe 5.5 weeks. She said they can see  a "sack" but can't see any baby yet but ovaries looked normal and took blood. She said "lets not get overly exited. 1-4 pregnancy end in miscarriage or are entoptic so come back in a week for another sonogram."
She also said dont what????
I mean should I be nervous? I felt that was a very harsh (although true) way to handle it. She wants me back in a week.