Talk to General Physician on Repeated Dehydration

I am student. I usually feels very low energy level before eating. It gets better after breakfast. High water intake and urination. I have repeated dehydration Symptoms Dry mouth Felling of dryness in body Not able to study General weakness ... Dehdration usually gets treated by fresh juices and i am getting these dehydrations after 1-2 weeks. ...... Is repeated dehdration sign of dangerous disease? Is low energy before breakfast dangerous? Is high intake of water and high urination dangerous? How can i avoid repeated dehydrations?