Colored lines on the screen

I did not drop my lgv2o and now when i stay on youtube for too long i get flashes or colored lines first just a few in random places across the screen. if i continue to stay on youtube my whole screen will fill with colored lines they are horizontal lines. the screen still reacts when i touch it but i cannot see anything. when i lock then unlock the screen it is still there but when i take the battery out of the back and put it back in and start it up everything is fine. ussually when i leave the youtube app it is fine but lately even when i close it out i am still getting the stray lines. What is it and how do i fix it?