Pretty common, it all just depends on how early in pregnancy the woman begins testing. It also depends on the type of tests she uses. Tests that detect hcg levels at 100 or over typically won't detect pregnancy until a week or more after a missed period in a pregnant woman with hcg levels that double normally. It really just all depends.

If you are a week late for your period and have accurate determined your cycle length, take a first response early result pregnancy test (I'd suggest buying a pack of two). If you get a negative, you have a high chance of not being pregnant, although some women's hcg level isn't high enough yet, but that is uncommon. If you still haven't gotten your period within a week, take the other FRER home pregnancy test. If you get a negative on that, then you can pretty much bet that you are not pregnant.

yes its possible however it doesnt happen often

hpts are most of the time (if used correctly) accurate

Happened twice to me -_-

you say it happened to you twice, if you dont mind could you please explain what happened, like how early you were testing and if the test were negative how you found out you were pregnant and how far along where you when you found out? sorry so many questions im just curious about it. thanks