Pregnancy test accuracy


I'm trying not to be anxious but here we go again...back on the wagon to have second baby! It took us close to 8 months the first time around. Anyway little late on my period (only 3 days) but usually pretty steady cycle but all pregnancy tests have been negative? Do you think I just have to wait longer and my period will show it can a test show a false positive this late? Has this been the case with anyone else?