I have painful sores on both sides of my tongue that come and go for 6 months now. I also have very dry mouth. Any ideas?

Sore, dry mouth. Tongue sores and dry mouth may be due to many causes. See your MD for assessment.
Lots. But a Dentist or Oral Surgeon will have to examine you when the sores are present to be able to make a differential diagnosis and establish a treatment plan. Please seek professional help.