Quoting firstname.lastname@example.org:" I know that FMU is recommended, but I am in my 4th pregnancy, found out very early on with all 4 and ... [snip!] ... the test. I say if it said negative, you probably aren't, but then again, I'm no doctor. Test again in the morning to be sure."
Not every woman has a significant amount of hormone in their bloodstream or urine for the test to pick it up that early. Just because you were able to pick it up that early doesnt mean that she will. Every woman and pregnancy is different. With my daughter i couldnt get a positive test until i was 7 weeks.