What is happening?!

So my period is late by 3 days now,I usually have irregular periods so I was like okay no biggie but why am I experiencing the exact same effects but without the blood? I'm exhausted,my breasts hurt,I feel nauseous and my legs ache.I know I'm not pregnant as this would be impossible considering I'm a virgin.

The main issue I have is that I have a performance coming up on the 26th February and on 28th I'm seeing my favourite band live.This is the worst time for this to happen to me!!!

I'm praying that my period comes before 20th as I have a 6-7 days cycle with pain and heavy blood for 1-3 days.