Hiya, congratulations on your pregnancy!

Just to add to what has already been said it is totally normal to feel that way. I know i did. I saw my
DD at 7+5wks due to spotting too. All was fine but at the 12 week scan i was still convinced they wouldn't find anything!

lol. I must have taken at least 3 tests. I also took at least 3/4 with
DS. we were only trying for such a short time (less than 1mth) that i was convinced it was impossible for it to be positive already! I think some of it is the hormones that are already present in droves. It makes you completely mad and paranoid (that's was my excuse anyway! lol)
As for whether the test would show positive if it was an empty sac it is a possibility but if you had had a missed miscarriage the test would quickly revert back to negative. All i can say is i would try and hold off testing over and over as it just makes you really nervous all the time. It gets expensive too and you will need every penny you can get in 9mths time! haha. I hope things all go well for you. Keep us updated Xx