How many weeks am I?

Originally I believed I was 6 weeks and a few days based on my last menstrual cycle Dec 24th. I had my blood drawn exactly one week ago today and the results showed my HCG level at 4007. My Dr. said I was 7 weeks, but the blood test was done the week prior, so does that mean I am 8 weeks? Also, my Dec. 24th cycle was short, not much blood and fairly close to my last cycle, which is usually always 28 days apart. So now I am thinking my Dec 1st period was my last cycle. I see my OBGYN today, so I know she can clear things up for me, but maybe you ladies can give me some peace of mind for the mean time. Do you think I am 6 weeks, 7 weeks or 8 weeks and why? I would like to have a better idea at the moment because right now I am just confused.