My Only Son Of 16 Years, Is Affected By Night

My only son of 16 years, is affected by night fall, so advise me what should be done to get rid of this. Moreover he admitted that he was addicted to over-masturburation for past 3 years which has weakened him a lot. This matter is of great concern because he will be appearing for Class X Board Exams. On 29 Feb’16 . Sir I need your prescription. We live in Calcutta