Question about my pregnancy! Please help!

Brittany • Baby boy was born April 21, 2015 at 21:49 weighing 6 lb 10 oz and 19 inches long!(:
Okay so I am 25 days late for my period and kept getting negative pee tests, so I finally broke down and went to the hospital for blood work and the dr told me I had 8 hcg in my blood and that he considered me pregnant. I'm confused though, I'm 25 daysate and only 8 hcg? What does this mean?