pregnancy or late period

Camille
Hello I took a pregnancy test yesterday it was negative. I looked at my tracker and I'm 2-3 days late. When I did the <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> on a different app it says my period shouldn't be here until tomorrow. I'm confused? Anyone else look at different apps and they come back different?