First off, you can sometimes just be late.
Testing early, false negatives are common. When you tested did you use your first morning urine (wake up pee)? It's important as it is more concentrated and more likely to give an accurate result.
Also, sometimes the home tests just don't work with all women
Wait another 7-10 days and then retest. hCG increases rapidly so it should be detectable by then, if it isn't now. If it's still negative and no period, see your doctor.