Talk to General Physician on Anxiety And Polydipsia

My son was very good at his studies and got good grades in the I and A Levels. In A-Levels almost one and half years ago, he was taking too much pressure and started having issues of extreme thirst and burning during urination if taken less water. Doctors at AKUH wrote many tests to diagnose the disease for all possible illnesses related to thirst like diabetics, liver issues, thyroid tests, diabetics insipidus, scan for the pituitary gland, etc. but all the tests are ok. I have an observation that he gets anxious to face every challenge like difficulty in his studies or fewer marks on a test etc. His thirst increases while he is stressed but also when he is not stressed but eats some food like oily, deep fried and oily fish, etc. This is very problematic. He is getting weak and tired. I will be grateful and keep in my prays for my whole life if any doctor helps me to diagnose the issue and get his problem resolved.