7 days late!

I'm 14 and I just started my period for the first time in December I had my next one 28 days after... <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a> says I'm 7 days late... I don't wanna make plans in case I start... anyone know why it's 7 days late... I know I'm probably irregular but I won't know what to do... I have never had sex 😶what is causing this...