Monitor screen goes dark for a few seconds

[doomstruction]

Hi, Today my monitor screen is going dark for a few seconds then going back to normal. It happens every 10 seconds or so and my head starts to hurt. I was playing league of legends and noticed the screen got a little bit dark then it goes back to normal after a few seconds. I then tried playing dota 2 and same thing happened, its like when i go to darker area of the map the screen automatically is trying to go dark as well. The screen does not seem to go dark when i open a bright page lol. Not sure, what the problem is but im using hdmi to connect cpu to monitor, could that be the cause ? i dont have any vga to dvi so cant connect monitor to graphics card without hdmi.


EDIT: I tried connecting with a dvi but the problem is still there. Screen goes dark when i open league of legend or any other game