Congratulations on completing your treatments! My husband uses the Biontene products - although even they were stingy immediately after rads.
It may help you to sleep propped up. The pain meds will either help you sleep or keep you awake - if they keep you awake, talk to the docs about it. Be sure to keep water next to you; if you don't have to get up to get water you may be able get back to sleep more easily.
I am glad to hear that you are able to manage fluids. If it gets a bit harder to swallow in the next week or so - don't be alarmed as the radiation is still hitting. About 10 days from the end, that will be over and you can begin to heal in earnest. Until then, sleep, take nutrition, read or watch movies, and be patient. We're rooting for you!