[ Pregnancy ] Open Question : Gestation week question?

I got my regular periods on 1st of Jan 2013 for five days. I got recently married on Jan 17th 2013. I found blood spotings from 27th Jan which went on for a week. so i decided to go for a pregnancy check on feb 8th 2013 and its +ve. The scan impression shows gestation sac corresponding to 6 weeks. I am confused as my marital status is only for 3 weeks till Feb 8th. Please clarify as to how the scan report 6 weeks? How is it counted? Is this counting correct. this is causing confusions betwen me and my husband?

Source: http://answers.yahoo.com/question/index?qid=20130216035956AAebGAL

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