Only measuring 6 weeks

So based off my LMP yesterday I should have been 7 weeks and 4 days. I went in for my ultrasound and the tech said the sac was only measuring 6 weeks and she really couldn't see anything because the way my uterus is tilted. I have to go back in 2 weeks and I'm going absolutely crazy. My dr is out of the office until Tuesday and I have so many questions. I'm not sure what to think. 
Update: Dr thinks it's a blighted ovum since my hCG is only slowly rising. More labs and another ultrasound to come. I still want to be hopeful but it's hard. 
Update: Last hCG done today and tomorrow another ultrasound. I just pray we see a beautiful baby and heartbeat.