What Could Cause Recurring Back-of-head Pain For 5 Years After A Head Injury?

Age :22 Gender:Female About 5 years ago i met a road accident.I fell on the road that hit back area of my head you can say back brain and it did not bleed.After accident i starting having pain in different areaas if the back brain and i am experiencing it even after 5 years of the accident continusaly .Some times it goeas sometimes it come.Sotimes it s normal and sometimes it becomes worse. I have my tests like x-rays,CT-Scan and EEG of brain and all tests were clea.Having medicines but nothing better Can you please guid me what can be the reason.