You could have Sjogren's syndrome, an autoimmune condition in which the body's immune system is thought to attack certain tissues in the body, including the glands that make tears and saliva.
Talk to your doctor about this possibility so that the diagnosis can be ruled in or out. He or she may recommend treatments to improve your symptoms or refer you to a specialist in autoimmune disease.
Have you had a significant injury to your head or neck? Have you ever had radiation therapy to your head or neck?