Period???

So I've had my last 4 periods literally every 2 weeks and TERRIBLE cramps and now I'm late by 11 days and have some God awful sickness in my stomach.. I don't understand why it'd be this irregular. I just don't know what I should do and my mom isn't taking it seriously enough to actually make an appointment, she keeps shrugging me off. I'm super emotional right now and more on edge and idk what to do right now :/ any advice?