[trouble]

Have you checked with your dentist to see whether your jaw joints (where your jaw meets your skull under your ear lobe) are equally strong?

My dentist found that one side wasn't working as well as the other and made me a custom splint (a mouthguard I wear at night) which trains the weaker side to work properly. It looks like the one on the right in this picture [0]. Since then, all of the pains on that side of my neck and upper back have disappeared.

The way you've described your pain seems similar to what I was experiencing, so maybe this information gives you something to go on.

One caveat though: my dentist said that the mouthguard approach doesn't work for everyone (about 30% of people get a result similar to mine) as it relies on fooling your brain in your sleep to train one jaw muscle to be stronger than the other.

[0] https://healthyheroics.com/wp-content/uploads/2018/01/orthod...