Absolulety no saliva in my mouth.feels nausea.what can be the cause?

Could be: Severe dehydration. If this is a recurrent problem, it could be one of several autoimmune disorders. You should see a doctor before it causes harm to your teeth and other mouth contents.

Medication: Some medications can cause a dry mouth. Are you taking any? Dry mouth is a serious condition that can cause a great deal of dental damage. I think you should speak with your dentist or physician to determine the cause and the treatment.