What kind of test was it (blue or pink dye) and how long did it take to show up. Also, when did you take the tests (morning, noon or evening). Did the test line have any colour to it as well, or was it a shadow/grayish looking. It could have been a true positive and you just didn't have enough hCG in your urine
I have actually had a false positive before, freaked out thinking i was pregnant, went to the gyno and foung out i wasnt preggers. take a few tests before you decide to go to the doctor. there still is a chance that you could be pregnant though.
take a few tests, maybe three. that one in the morning, one at lunch, then anoth the next morning. are you late or having symtoms (symptoms) of pregnancy? untill you know for sure, just treat your body like you are pregnant, like dont drink alcohol or anything.