starts to implant, so an early-detection pregnancy test will be positive, yet it won't attach properly, and will be shed with the lining shortly after. I guess it is very common
, but most women won't know because they just assume their period was a little late.
They say that's one of the bad things about using very sensitive pregnancy tests. You could actually detect a chemical pregnancy early on in your cycle, which you normally would have thought was just a regular cycle...and then have to deal with the emotions that comes with knowing that you were in fact pregnant.