Headaches after Anterior Cervical Fusion

Dear Dr.

On Aug 3, 2009 I had an anterior cervical fusion, with spinal stenosis, removal of bone spurs of C 4,5,6. He also adjusted my cervical column as it was shifted to the left as well as had a bow in it at c5&6.  I was home in 3 days.  I am physically fit, thus, no collar or PT prescribed for me. However, my doctor discussed changes in my exercise routines.  Not a problem.  I have been off of the vicodin since August 20th as i am allergic to codeine.  

I still have muscle & nerve spasms in my shoulders, upper back, and arms.  This pain I manage with NSAIDS & ice packs.  However, for about five days now, i have had this spot headache on my left side of my head.  Last time I talked with my surgeon about the headaches he said it was due to withdrawal of the vicodin.  at that time i was taking the vicodin regularly.  

What is causing these headaches as I cannot sleep properly nor may i move about as it makes me dizzy & ill to my stomach?
Thank you Edie