Took a 500 mg acetaminophen for a headache, i'm now nauseous, headaches worse and moving around, dizzy, almost fell over when i stood up. what's up?

Changing headache: Headaches can be a concerning symptom and can have many causes. Some are deserving of EMERGENT treatment. Warning signs are chronic headaches that suddenly change in quality or intensity, multiple headaches a week, new onset headaches that affect one's ability to function, associated vomiting, associated dizziness/double vision/neck ache/fever/weakness, or the need to take daily pain medication.