The weeks estimator is a guesstimate, so it doesn't necessarily match up to gestation. Also, I do agree that you could have just ovulated a bit later than suspected. Women do have early pregnancy bleeding and I'm glad your doc had you in. They really need to be doing a beta 48 hours apart AND scanning you next week. If you are 6 weeks, they could have and should have scanned you when you went in. At 6 weeks, you should see something even it its just a sac. Most of my pregnancies had measurable heartbeats at 6 weeks.