i did the samething when i got pregnant, the reason mine didnt work was because i didnt pee on mine enough (i had just taken one and was in such a rush that i didnt wait till i had more pee lol) it could also be that there was too much urine on it!
i researched them and from what i found is they arent positive but fairly accurate because the test your ph levels and if it shows more acidic your chance of a girl is higher and alkaline for a boy.. this is only if taken first pee of the morning on your normal routine. we didnt have the test in...