I fell today and hit my head pretty hard its been 4 weeks and ever sense I randomly get headaches and get super tired. What's wrong?

Concussion. If you hit your head hard 4 weeks ago and then started having these symptoms you may have sustained a concussion. Take care to avoid another injury and go and see your doctor for an evaluation as there are some other possibilities and considerations.
May be Concussion. Please see your doctor as you are describing what may be a concussion. Symptoms generally resolve within a few days, but lasting as long as yours are it deserves an evaluation.