Recently, I've been having an ongoing headache, as well as stomach aches and abdominal cramps (I'm 15, and a guy.), and I assumed it was a stomach flu, and that i'd be gone soon, but right now, I still have a headache. At night, I begin to get really cold and shiver, even though it's warm in our house, about 73* F. Then, when I wake up in the morning, I'm shivering in a cold sweat.