Laptop screen goes black, but LCD panel is still lit up

I have a Dell Vostro 3560, i5, 1gb graphic card, windows 10 64 bit. Automatic updates are on, and hopefully everything is updated. I started experiencing a problem, where the screen will go black, although its lit up (you can see black screen with light coming out from edges), so its not switched off, but nothing works. I have tried to hold down power button for over a minute and it wont switch off. So i need to plug out the power supply and batttery and reboot. In particular, I have tried to reinstall (Clean uninstall in safe mode) the display drivers (intel and amd both), opened up the casing and cleaned the cooling fan, changed the thermal paste, but nothing works. I usually get this blank screen when I am projecting a powerpoint lets say, and the moment I press windows P to extend or duplicate, it goes blank (laptop is already connected to projector and display is extended, and then I wish to change it to duplicate). And other times randomly it goes blank. Please Help

Update: I just ran the diagnostics, (BIOS), and CPU temperature averages 65 and graphic card averages 43