Help Please! 💔

By calculation, im 7 weeks pregnant. Home and blood tests positive. Went to my first Dr. Appointment and they didnt find anything in the U/S. We are devastated. Our doc is not very positive about this. I have not bleed, but he says it could be an empty sack or im about to have a miscarriage.
Last option is that is too small to be seen. Im freaking out. They took my hormones test yesterday and im going back tomorrow to see if they duplicate. 
Has this happened to anyone here? 
I could really use some advice here! 😭