How to help my husband who is in constant pain

My husband was diagnosed with throat cancer in July last year.  He went through 7 week chemo and radiotherapy. He got through the treatment well, however a few weeks after the treatment ended he has been in constant pain. His tongue is very tender due to the radiotherapy, plus the whole side of his mouth. On the other side of his mouth, the bone is coming through. It’s been weeks now and he often struggles to eat and talk. He has a pain management repeat prescriptions, however, the doctor often refuses to refill the morphine and ibuprofen saying that there hasn’t been enough time from the last prescription for him to get it. He then has to go a few days without it and of course that means his pain is amplified.  I am trying to get the prescription issues sorted, but I don’t know how to help him. It’s so hard to see him in constant pain. He is so tired and also really fed up with it.  I can talk to the nurse and GP about the pain management and eating issues, but I have no clue how to help him feel better. I feel totally helpless and also exhausted from it all.  To top it off, my brother passed away from prostate cancer less than a month ago.  It’s all a bit much. I know my husband is the one going through debilitating pain and we are still waiting on the outcome of the scan to tell us whether the treatment has worked or not. Is there anything I can do to help him?