Dry mouth symptom

I suffer with a dry mouth which gets worse in the evenings - I am chomping my mouth and smacking my lips - and long for the relief of going to sleep. I sip water and moisturise my lips regularly but symptoms persist. It is debilitating.
I take Tecfedira twice daily for my relapsing remitting MS.
My MS nurse and neurologist dismiss my symptoms as unrelated to MS/ unimportant!

I’ve suffered with a dry mouth since December which was brought on by a thunderclap headache, nerve damage in my head due to demyelination. They first thought it was Sjogrens but after having ultrasound of saliva glands that was dismissed and was told it was ms that had caused it. I’m still suffering with a dry mouth and after a further two relapses my mouth is even drier and the numbness had spread. I now use a special mouthwash, toothpaste and drops to ease my symptoms. Chewing gum helps , but as you probably realise it can make it difficult to eat and talk when your mouth is that dry. Also it makes it harder to obtain nutrients from your diet.