Need advice ASAP

So for past 4 days my apetite has decreased to the point i could go an entire day without eating just about remembering fluids. If i eat i will vomit even if its just pot noodle. My stomach is cramping badly and i dont know what to do. Im naturally loosing some weight and feeling extremely weak. Should i see a doctor or wait it out. I have been having trouble sleeping as well. Period is due on the 28th