Wtf?!?!?!?’

I need so help ladies! I am in the middle of my fertile week and last night I started bleeding, I’ve been having some bad stomach pains and this morning I woke up and basically started my period... Ive never bled in the middle of my fertile week and idk what’s going on... I started my period when I was 11, I’m 18 now and this has NEVER happened. Can anyone tell me what’s going on?