I have had the exact treatment you have had.  I was diagnosed in February, 2008, underwent a bilateral mastectomy in April, 2008.  4 treatments of cytoxin and taxotare which ended in July. 2008.  My headaches and dizziness began in February, 2009.  Extreme and daily.  I have had 3 MRI's, all negative, a CT Angiosomethingorother, as well as, 3 occipital blocks, which numbed my scalp, but did nothing for the pressure and pain.  I continue to battle head and neck pressure and pain.  Every day.  I wish someone could give a diagnosis.  If it is a result of the chemo, so be it.  At least we would KNOW.  I wish you good health and days free of pain.  C