7 weeks or 12 weeks

Betsy
I'm not sure which!
My first positive was the day before Easter. So I went to the (general practitioner) Dr. for a blood test that Monday. When I got the results they said the numbers were low, likely because it was still so early, 2-3 weeks. So I was instructed to come back in 3 weeks to do another test.
Well that was yesterday. I got the results today and they said my numbers were high! They think I'm around 12 weeks according to that!
My LMP was March 17, but it was about 4 days late (with negative tests at the time!). This would make me 7 weeks 4 days. 
I'm not sure what to think! 7 weeks? 12 weeks?!  
I plan to call the OB tomorrow, but my first appt there is the 26th!