robin williams spent his last days in a paranoid frenzy , aware that ` something else was wrong with him ' , a british television show will claim tonight .
the 63-year-old , who had been prone to episodes of insomnia and anxiety prior to his death , also spent his final 24 hours frantically looking up drugs online , convinced he had another illness .
williams hanged himself in august 2014 , a death which sent shockwaves through the celebrity world and led to an outpouring of grief from his worldwide fans .