Pegestrone low!!! So worried!!!

Laura
Last week i had my first ultra sound, come to find just a sac. I had so much blood work done and they said I'm only 4 1/2 to 5 weeks along verses 10 weeks like they thought. But now they are so worried my pegestrone is too low so I'm freaking out hoping for the best. Any one else have anything similar??? Any advice???