I’ve read up to 45% of radiated head and neck patients have sleep disturbances. I had same diagnosis but did chemo and 33 rounds of radiation. My sleep has definitely changed, with most days up by 4:30am. Tried numerous meds for anxiety and did not like any of them. I tried music therapy and deep breathing techniques and have had success! I still wake early, but go to bed early and sleep about 8 hours. I too, take 10 mg of melatonin and use CPAP. Try listening to Southwestern Indian flute music and breathing deep and slow !