Suggest Treatment For ADD With Sleep Disorder And Lack Of Concentration

My son age 12+ , at the age of 10 we notice he is suffering from learning problem which we got information from school teacher, We contacted to doctor at the age of 11 and she diagnosed ADD advice to take medicines Methyl Phenydate as 5mg tab then 10mg tab later sr20 and sr30 in morning and 10mg tab at afternoon . During the treatment we observe much improvement in terms of concentration. But facing problem in exam/class became very slow. sometimes forgetting things. Mainly now observe nervous, forgetting, asking to have medicines before study. Sleep disorder and appetite problem is there, sometimes facing problems with eye(blurring vision). Now he facing problem with examination in school, He knows everything doing very well in home but not able to write or mistake like incomplete answer specially in maths. He know maths doing correctly but inbetween he is miss some figure unknowingly even he not able to find at the time of revision but after time is over he can understand what mistake he done. please help on this. He is doing well in other subject other than maths.