Headaches and neck spasms

I am 33, and after 17 years of chronic headaches/neck pain/back pain, and after countless visits to doctors, chiropractors, physical therapists, acupuncturists, and massage therapists, I am so happy to find Esther's book!  I believe that most of my pain has been due to poor posture, and then mis-correction for that posture, which in turn created new back issues.  In addition, I have some stenosis and bone spurs between C6 and C7.  So that's enough background info--on to my question.  I have been using the steps in the book for about a week, and have had really great results in my low to mid back area.  I no longer have numbness down my legs when I sit, and can alternate between stretchsitting and stacksitting when I start to feel discomfort in my low back.  However, I am getting muscle spasms in my neck, which is causing some pretty good headaches for me.  I am really trying to roll my shoulders and relax them, and to straighten my neck then relax it, but after sitting at my desk at work for a couple of hours my shoulder/neck area is really spasming.  Is there something I should be doing differently??