Suggest Treatment For Acute Psychosis

My son has been diagnosed as having acute psychosis. Two different psychiatrist have prescribed for him, 5 mg daily of ZYPREXA (olanzapine). He is 20 years old. His symptoms are : has lost interest in almost everything, does not go out at all, stays in his room all the time, he is not aggressive, We have asked him if he hear any votives or see things but confirmed that he does not. He sometimes utters continuously but softly quote I hate you, I hate you ... . By you we think he means his Father (that s me) and his mother, and maybe his brothers. He has three elder brothers and two sisters, he is the youngest. When we ask him why he does not reply. He does not sleep the whole night but start sleeping early in the morning. He take so much time eating, slowly nibbling, and just watching his plate. He sometime tends to wash his hand every time you try to talk to him he always excuses himself by going to wash hands. He has to be continuos reminder to have a shower, he takes a long time in the shower. He is almost expressionless. When he was young he was quite a shy boy. Did not have any friends in school. He graduated from high school with great grades. He joined a university in UK in September 2012. He did well in the first semester, but started to not miss classes in the second semester, and had to resist three exams which he did and passed. But the beginning of the academic year 2014/2015 he could not attend all the classes for almost two months continuously and had to stop studies and come back home. He is back home in UAE since Dec 2013? He does not want to take his medication, and we do not want to force him, but the Doctor( psychiatrist) told us that any delays in taking his medicine will worsen his condition. He does not accept that he is not well. He is always with his iPhone and if seems he has read the side effects of the drug and urges that it will destroy his brain. very worried with the side effects of the drug. Is there any other alternative medicine? Should we get another assessment? Is there any chance of misdiagnosis? What should we do. Please help.