An ANA of 1:40 can happen with healthy people, I have been told by docs. The 40 is a low value. I have seen it termed low positive or negative on different sites. "Mitotic" is a less frequent pattern apparently.

I had an ANA of 1:5280 and even that is not conclusive for an autoimmune disease. One of my kids has 1:80 with no illness at all.

In my experience, neck issues can cause headache, neck pain and shoulder pain. You could have an MRI of your neck. I have various diagnoses with those symptoms and PT massage has helped.

If you are having fevers, that is concerning and I am sorry you are sick. There are a lot of causes for fevers so it is hard when things are mysterious. I hope your doctor can help you clear things up. It may take some time!