My iphone6 started to flicker then went black, its on i just cant see it

I was just on youtube, when the screen on my ihpone 6 (128GB) started to flicker then white thin lines appeared all over the screen (vertically) and then the screen went black. It's still on but I cant see the screen as its black and doesn't show anything.

No I haven't spilt water on it or any other liquid.

No I haven't dropped it, nor is the screen cracked, scratched or damaged in any way im very careful with my stuff.

I just need an answer, or at least an idea to what has happened, thank you.