My Eyes Get Very Dry, Especially When I Sleep. When

My eyes get very dry, especially when I sleep. When I put just plain saline solution or resetting drops in my eyes, it sings. I wear contacts during the day so I am very careful to not use anything that might not work with them. Tonight alone I have added drops to my eyes (without there contacts) to help wet them about 4 times. Each time it stings. It is rewetting drops for soft contact lenses.