If you are on certain medications you may get a false positive. Have you had unprotected sex in the past 4 weeks? If not then I would trust the blood test, which is far more accurate than a urine factory pregnancy test.
hey dont worry!!! those pregnancy tests are not always accurate it happened to my sis and in the end she wasnt pregnant at all so dont worrry as long as u did a blood test and it came negative then ur safe lol am a nurse and im scared like hel to lose my virginity cz of the pain hahah