I am dealing with this through a very good friend of ours! Very sad. She was briefly hospitalized recently and has been dealing with terribly severe headaches for 3 months to the point that it has basically halted her life. She, too is on an addictive-type heavy duty pain med.
Her dr. recently agreed to let her get an an MRI (please don't ask me WHY they haven't done one sooner - it's been a ridiculous path that she has had to take to convince her dr. that she needs an MRI! - Good insurance - no health concerns would restrict her from having one.) She is awaiting the results. She has had a CAT scan and it is normal.
What she does know is that her neck is very straight - lacking any normal curvature. She also has been recently seen a dr. who believes that she is allergic to gluten and possibly dairy and is taking the necessary steps to eliminate this from her system. She does see a chiropractor, however, he could be aggravating her condition without knowing it - because of the lack of MRI.
Very sad for your friend. I hope she gets an MRI - it can stem from the neck, sinuses, allergies, etc.... My sister eliminated dairy from her diet, because her dr. believed it caused her the severe sinus problems/headaches. She has been free from them for a year. Also, trying to just briefly eliminate gluten (there are still so many things you can eat that don't have gluten). If she is a carb-a holic or loves dairy,sometimes it is what you crave that becomes what you are sensitive in, so, I would definitely look at her diet.
Please keep us posted. Thanks for caring!