hello , thanks for the query .
The dry mouth
you are experiencing could be due to various causes such as side effects due to certain medications like antihistamines , pain killers , antibiotics , nerve damage
, diseases like diabetes
, fever can all result in this .
I would suggest you to take plenty of fluids , use an oral rinse regularly , avoid spicy food and consult the doctor for treating the cause . The pain in the back could be due to sciatica
. it is best diagnosed using an MRI to find the cause . painkillers can also be used to relieve the pain .