Late period for no reason ?😭

Jeniffer🦄
So I got my period on July 12 2016 . And according to <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a> I'm supposed to get it August 9 , but until now I didn't get  it . I'm single and never had sex . Can someone please help me ? 😭 what's the reason ? Btw I don't have a doctor that's why I need your help ! Thanks. 💖✌️