When I turn my laptop on it only shows white.

This is a display issue .Either the screen has gone or the cable is broken or disconnected . If your comfortable opening your laptop check the cable first making sure its connected properly at both the motherboard and at the video screen. Also check the cable itself where it goes around the hinges . Check here for cracks. feel the wires they can sometimes break inside the coating and not appear broke but be faulty . If your satisfied the cable is fine then you will need to replace the LCD . Before going there play around with the resolution settings of the laptop using the external monitor . As this is a gaming computer some games actually will change your default settings to accommodate there game and there is a chance this has happened so change your resolution settings around and see if there's a difference. Hope this helps