No sac at around 5 weeks ultrasound? :(

I've had bloodwork done and it's pretty much tripled every 48 hours. Saturday ot was 1249 which puts me around 5 weeks. At that rate today i'd be over 3000 hcg... I had a transvaginal ultrasound and they couldn't see a sac but saw what they THINK could be a sack bit it must be too early to tell. My LMP was 7/9 which they think puts me over 8 weeks and i let them know according to my blood work im not that far along. I went to a pregnancy clinic for a free ultrasound since finding out I'm prergnant before I go to my first doctor appt and ultrasound with then on the 22nd so I have a couple weeks I'm hoping I see something then! But god I can't help but worry and pray everything is okay ;( Has anyone dealt with this? :/