Someone explain!

I got my BFP last Tuesday the 15th (yay!) and I got bloodwork done to confirm and my levels were at 23 so they wanted me back on Friday to make sure they are doubling. I found out today that my levels were at a 90 on Friday so that's good! Now this is where I'm confused. I asked how far along she thought I was and she said I'm right around two weeks. So she's pretty much saying I found out I was pregnant at 1 WEEK. So I asked if she meant 2 weeks actually pregnant but 4 weeks total including conception and she said no 2weeks total pregnant. How is this possible?!