I would be up until dawn,and then sleep for 14-20 hours if it wasn't for Zopiclone. (I think there is another name for this that starts with an O?)
I also see a couple of shrinks that talk about good "sleep hygiene". But they have never had oral cancer or depression.
My husband is very understanding, but I have trouble sleeping in the same bed as him with my mouth taped shut and then the gagging on mucous in the morning.
Sorry to paint an awful picture - but it's only my own self-portrait. Not yours.
See your GP or PDoc to see if they can help. Physical therapy also helps a lot. Massage was wonderful for me. You are not long out of treatment so maybe it's just a matter of time to get back to the new normal