Confused

JB1971

This is my first pregnancy. The first day of my last cycle was July 15, 2012. That was four weeks ago. Thebump.com, however, only shows that I am 3 weeks along. Why the difference of a week? I took two tests and both showed up positive, but I still almost barely believe it's real. According to the website, at week 3 it's usual to get a positive response. Any advice? I am unable to see my dr. until week 10, so I have a nice wait ahead of me.