Would it be better to consult a d.c., a d.o., a d.p.t, a neurologist, or an orthopedist for the chronic pain & stiffness in my back, neck and head?

Not an easy question: All of these deal with the pain you are describing. If you cehceck with your family physician already, you may want to move on to the orthopedist or neurologist. D.C and DPT can help with the pain once diagnosed. Do get checked and don;t let the chronic pain go too long.

Pain management spec: A comprehensive pain management specialist can help with the diagnosis and management of all aspects of your problems and refer you to the right therapist, chiropractor or surgeon if needed. Look for a pain specialist who is board certified.