I have had sharp and dull stabbing neck pains for over 30 years. I've had therapy and chiropractics to no avail, and no reasonable diagnosis. Help?

Further work up. Further work up may be indicated if not done already, i.e. Cervical spine xray and mri. You might benefit from certain types of medications that help with "nerve" pain. Injections may play a role in managing the pain if you have had no relief with physical therapy and chiropractic treatment. See a spine specialist/pain management physician for further evaluation and treatment options.
Arthritis. The number one reason for chronic neck pain is degenerative changes of the joints (facet) of the spine. If no arm pain is involved, then disc disease is probably not involved. If conservative treatments like pt and chiropractive manipulation cannot reduce the symptoms, then injections around the facet joints should be tried next. Will need a MRI to make sure something else isn't causing issues.