What Causes Headache,nausea And Body Tremors?

hi, im 18 years old. i have been feeling terrible. every morning and every night around 1am i begin to feel super nauseous, coupled with headaches. this nausea has lasted for over a month now. i feel really shaky, and i have headaches. i dont have a fever, but i feel like i am going to get one. i feel very weak. what could it be?