I hit my head 3 days ago and i have a headache that is getting worse, nausea, extreme tiredness, and dizziness and can't focus. what should i do?

Closed head injuries: should be evaluated in the ED to ensure no significant structural intracranial damage has occurred. With your symptoms it at the very least suggests a concussion if not cerebral contusion. Get evaluated soon.

See a doctor!: Hi. Closed head injury can be very serious! You could have bleeding that produces a mass effect and pushes the brain places it really shouldn't go! See your doc and get a head CT...no harm done if it's negative, but it can save you untold woe if it's positive for a bleed! Tschüss!