Pain in neck, collarbones, shoulders, upper back and arms. Ideas?

Eliora, I would see a chiropractor. You might make sure they use the Palmer method; I think it is the best. And they do the most thorough manual exam. They are much less expensive than neurologists and orthopedists. And you can usually get in to see one same day, at least same week, without a referral unless your insurance requires one. I see chiropractors often and get great and immediate relief. Some people are afraid of the adjustment, but even if you don't accept the treatment, you know more about your situation after the consultation. Sometime the shift in the spine is so small that it isn't apparent on an MRI and wouldn't be anyway when you are free of the weight of our heavy heads while lying down.
I hope you have luck.
You could ask for a CT of the neck and shoulders which would give you more information about soft tissue than an MRI would.

Eliora,

First off - I love your name!!

You are too young to live in pain without answers! I made the mistake of living with the back pain from 28 until I was 60! Please advocate for yourself and get answers! I would highly recommend you add a rheumatologist into your bank of doctors and get in depth bloodwork! I found out at age 60 that I had been living with rheumatoid arthritis, undiagnosed for many years.

Prayers that you get answers and relief!

@gently
Thanks so much for the well wishes and for taking the time to reply! I am really curious about one thing you said— What exactly do you mean by a small shift? Is there a specific condition or issue you are pointing towards with that? Neck instability? Jammed joint?

@dadkins
Thank you so much for the kind words, the prayers, and the encouragement! I really appreciate it. 😊
Interestingly, I actually went deeply down the rheumatology rabbit hole over the last year.
My journey started with knee pain after falling off my bike. Over a span of about five years, I had multiple MRIs (back home) that didn't catch any mechanical issues, so I was actually given an autoimmune diagnosis back home. It was a really tough journey-| even took
Methotrexate for two to three months. It did absolutely nothing for my knee, and left me with stomach issues and feeling the worst i felt in my life.
Later, decided to do an evaluation in germany, a rheumatologist and the hospital rheumatology department there sent me for a MRI, but this time on a higher-resolution 3-Tesla machine. That scan finally caught the real problem: a mechanical meniscus tear and grade 2 degeneration, with no signs of arthritis. Between that imaging, my blood work, and the clinical signs, the autoimmune diagnosis was officially debunked.
Because of that traumatic history, when this sudden neck pain started, my mind immediately jumped to it being an autoimmune condition.
I had my CRP and ESR checked right away, but they were both completely normal. So, while I am so glad you finally got your answers and relief, it seems highly unlikely to be an autoimmune condition for me

@velvinyl,
the neck moves in six directions in three planes. We have two tiny joints at the side of each vertebra to help them move smoothly. A tight ligament, tendon or muscle can alter the balance and trap the vertebra into an such a slight off position that eventually it does show up on MRI as osteophytes (bone growth) or arthritis.
Sometimes we have an injury to a lower part of the body (like the knees) that alters the balance in the way we walk or stand. That imbalance affects the spine all the way up the spine.
Untreated, over time, those imbalances adjust the muscles to maintain the imbalance. That imbalance can become stable, but still may be pinching the nerves that exit the spine. In some positions you don't have the pinch.
My thoracic vertebra shift and hold slightly to the right which affects mainly the 4-5, 5-6 cervical vertebra, the ones that give a person the shoulder pain and burning you describe.
Chiropractics may not be an answer for you, but it is so easy to try. Some chiropractors are moving away from manual adjustments to mechanical means of adjusting. You might make sure their method is manual before scheduling.
While relief is immediate physical therapy and massage help maintain the adjustment.
If you ask a lot of questions, they'll tell you everything about what misalignments you have and what exercises help maintain balance.
I hope it works for you.

@gently I would love to hear a bit more about your story to see if our situations align, if thats okay with you
How did your pain first start? Was it suddenly, or from a specific injury, or did it just slowly build up over time? Also, how did you or your doctors finally figure out that your mid-back (thoracic spine) was the cause of your neck and shoulder pain? Is it through the osteophyte on mri that you mentioned? Do you hear clicking? (A doc told me i should get checked for neck instability cause of the clicking..) I am trying to piece my own puzzle together, and hearing how your symptoms progressed and how you got your diagnosis would be incredibly helpful!

Eliora, at the risk of boring you:
It did start with my knees. No help from imaging or from doctors. Arthritis they say, which is basically what you've already told them when you say you are having problems with your knee joint.
Seeing a chiropractor was something I didn't put much hope in, but then the first chiropractor I saw adjusted my knee, but said the problem originated in my sacro/iliac joint. We have two on each side.
When this joint doesn't move smoothly each step on the lock side hits the ground a little harder because it makes that leg a fraction shorter. And that offsets everything all the way up my spine. I feel it the most when it reaches the top of my spine. Those two top vertebral misalignments can cause dizziness and nausea. I'm careful to get adjusted when I feel it in the SI joint.
I had a rough year in Chile because I couldn't find any chiropractors there.
This is a general spinal nerve chart might give you an idea of what level might be involving specific pain https://stlouispainmanagement.com/spinal-nerve-chart/
C6 and T1 seem to be the cause of some upper arm pain.
I've seen really good chiropractors and some that were ok. I've never seen a bad one.

I'd thought to mention this when you spoke about the click when swallowing, but I couldn't remember exactly where I'd read it.
https://ubiehealth.com/doctors-note/clicking-throat-hyoid-bones-pops-medical-follow-47

Get all the best professional help you can…try to get at the root of the problem…docs have a hard time with these types of things…i had better luck with my DO/MD and expert PT….in my case, it was occipital neuralgia, pain running along those nerve pathways…low-dose amitriptyline, 10mg, helps some…Tylenol takes the edge off…heat can help…special exercises ….no need to live in constant pain if you can alleviate it …surgery would be a last thing to consider, but can help some people……one thing that can help is keeping your head above your shoulders, as constant bending it forward will stress those pesky nerves

There could be any number of reasons for the pain and weakness you are feeling. One would be a pinched nerve, but like everyone else here I can only guess and I wouldn't call it an educated guess either. There are so many things it could be. Your age rules out the probability of a few things that generally affect older people. A good chiropractor might help but a bad one could make it worse. If it was me I'd find a neurologist at a teaching hospital and get blood work to check for inflammation.