positive test then negative??

did a test about a week ago and it was positive, (one of them digital ones) so i went to the docs and got a blood test ect, get the results tues... but did another test last night (digital one) and it said negative... got all worried and went and bought another test from the supermarket last night (one of them midstream 'confirm' ones) n did it this morning and it was negative too :( ?
looked some stuff up on the internet and it said that a lot of early pregnancys end up chemical pregnancys, so like early miscarriage?

i cant wait till tues to find out if im pregnant or not?! well i suppose i have to, but if it was a chemical pregnancy, why havent i got my period yet and why am i still sick and gettin headaches ect?

just want some feedback, no idea what to think! :doh:
sorry about raving on lol..