I always get really bad headaches and nausea.o experience this for around 2 hours at a time. i was wondering what the cause of this and how to prevent?

Different types: The 2 main causes of headaches in your age group would be migraine and tension type muscle contraction headaches. Either one can have associated nausea. Migraine often has a preceding warning(flashing lights, etc) and is usually a one sided throbbing headache while tension type headaches are usually steady over the forehead or back of the head. A neurologist is a headache specialist as well.