late period

My boyfriend and I have recently had sex, but my period was due 5 days ago and I have still not come on is this normal??? I'm scared as I don't know what to do because it's never happened before, but this is the first time I've used a <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> and my period did last for 7 days