Hello: My husband was on Opioids for three weeks and lost weight, lost appetite, and had difficulty staying awake. When we transferred to Mayo Clinic (for 3 months opioids were not used. Thank goodness.It was a challenge to find food he liked. He slowly began to gain weight.
I encouraged him to listen to Dr Amit Sood's Mindfulness tape that I listen to regularly. Although both of our medical issues are much different from yours...the lessons learned about how to really relax eased each of our very different pain. Dr Sood has written several
books that are a interest read on the Body, Brain & Mind connection which has helped me heal and deal with breathing.

Our body often need time to heal and if we can learn to incorporate mindfulness and tell our brain to ease the pain and relax
our nervous system we can heal better. I wish you all the best. Oh, Dr Amit Sood has done some entertaining yet helpful talks
that can be found on You Tube. I hope this helps.