Being only 3 weeks out, one would think more pain meds would be an option.

Do u have weakness in your shoulder and biceps? That might resolve since your surgery was so recent.

Once more time has gone by, if your pain is thought to be due to spasms, consider Botox. I have neck and central shoulder spasms after a C5-T1 fusion and decompression surgery. I used Valium for a while, but it began to affect my memory. Botox has been a godsend. They may want you to wait at least 6 months though. Ask about baclofen or Valium if you think it’s spasm related.

If you are allowed to get wet, a nice warm soak in the tub with Eason salts and whatever essential oils you find relaxing (I like lavender and lemon, or eucalyptus) might help.

If the burning pain is neuropathic pain, they make an OTC roll on lidocaine that you can use as often as you wish. I had limited luck with it. I attend PT at a Spinal cord only PT center and others have found great relief with it. Make sure to get the maximum strength. I have enclosed a pic from Amazon

C5C6 and C7 innervate the diaphragm. Are you having any shortness of breath?

Have hope that many of your symptoms will resolve as time from surgery increases, though it may never be as it was pre-op.