Thanks for using this forum....
Head injury can lead to some amnesia and memory loss which gradually returns to normal in 6 months to one year...The memory loss is also due to lack of attention due to depression which can be taken care of with drugs...Back pain and stiffness will require a thorough examination to rule out back problems...You can visit a neurologist to help you out..The silver lining in head injury is that as time passes head injury symptoms generally improve considerably...
take care....