Xerxes has been to the doctor numerous times for various ailments but the doctors can never find a physical cause for his symptoms. which type of disorder does xerxes most likely have

If there is no physical cause for any of his symptoms then it's likely that Xerxes has some form of mental health disorder which is causing him to experience various ailments. Mental health disorders can cause very real physical symptoms of illnesses in people and it is important that medical professionals are aware of this. It is also important that medical professionals do not write physical ailments off as just emotional health issues as this isn't always the case if they can't find any physical reason to a patients problems. It works both ways.  

9, 5, 10000000 ( that is supposed to be a ten for the last one)