ultrasound and internal ultrasound done

When for my scan today, worked out to be 12 weeks 5 days but they couldn't find anything and then she said no evidence of a pregnancy greater that 5 weeks, had to do another test and it came back postivie, so I've got to go to the hospital and have my bloods done, but I'm just confused what does no greater than 5 weeks mean I'm pregnant or not?  Also had no bleeding, I had spotting in September and they told me there's a chance I could of been pregnant in September and lost it, but I've had  so many positivism tests, no bleeding for at least 3 months either