Period

Yesterday my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> said I was supposed to start my period in three days, and just today it asked me if I had started my period , does that mean my period is late??? I had sex without a condom yesterday, and last month I started on the 12 . Help I'm kinda panicking .