Necks are problems waiting to happen, if you ask me. Everything gets all constricted into this tiny place. Think about it. Several bones held together by ligaments, cushioned (hopefully) in between. Blood vessels, every single nerve that goes to your body. Your airway. The route to your stomach. Throw in a couple of glands, a ridiculously complicated pair of jaw joints, muscles, an incredible array of nerves for feeling and tasting. Lots of muscles, each of which is subject to tension, and will try to compensate for any misalignment. I'm sure Diego4Life could add a bunch more.
Worse of all, instead of being out looking around for predators or prey, some of us sit in front of a computer monitor all day in the most unnatural position possible. I have lots of the same symptoms you describe.
"Pain in the neck," is an expression for a reason. From your chest up can be tension city.
You've been reporting a lot of symptoms consistent with stress, in my opinion. Whatever you have been doing isn't working. Maybe you should look at how you are spending each day and see if you can make changes.
