It's a nasty problem, especially when chronic. I hope you are able to find something to mitigate it, AND I hope it eventually improves.
Be aware that if your mouth chemistry has been altered, then your saliva may no longer protect your teeth very well anymore either. Don't be surprised if you have a sudden surge in cavities, etc. ๐ข
This is a common problem for people on chemo and many other medications, and also sometimes just a medical issue on its own.
You should be able to purchase nasal lubricant sprays or gels off the shelf at your local pharmacy. Oral ones are avail too.
BUT โฆ at least in my part of the world, these are often just not avail. Unsure if always sold out now or supply-chain issues. ๐ฌ
Likely Jan Lukas