5 week and only a sac

I am super stressed. Iv been doing home pregnancy tests all week and they call came back super dark positive. However i had my ultrasound today and they said they only saw a sac and nothing else. They asked me to get blood work done and come back for ultrasound next week but for now they only saw an empty sac and no yolk or anything. Has anybody had that happen i am soo stressed worried and sad. Dont know what to think of this

Can anybody share their experiences . Might help with my anxiety :(