With a First Response test, you want to make sure to follow the guidelines for early testing (and also check out the percentages of accurate results as they change drastically in just 48 hours).
As of the time I'm answering this, you're now five days away from your expected period, and this is the earliest a First Response test claims to be reliable, so if you took one earlier than today it wasn't accurate.
Go ahead and start testing today. Personally, I think the best way to test early on is to use the dip method (pee in a cup and dip the test) that way you can make sure you're immersing the test strip for long enough, giving you a better chance of a reliable result. If it comes back negative, try not to fret. It's still really early to be testing! Take another one on June 27th. If that one is negative, wait again to test until June 29th.
The reason for testing only every other day is that pregnancy hormones double every 48 hours in early pregnancy. So, if your hormones aren't high enough to be read today, they may be much higher in 48 hours.