laptop screen blank

Hello.
I have a Hp pavilion notebook. one day i was working with it, put it in sleep mode,when put the lid up again the actual screen was really dim for some reason. i tried moving the monitor back and forth, then the screen got normal again.
few days later, i turned on the laptop to find that screen is blank! i could see the light in screen changing whn the laptop was starting, but couldn't see the actual screen. i tried using it with an external monitor, and it worked. i tried using some techniques like holding the power button for thirty seconds and plugging in the charger, but nothing worked. So I left the laptop untouched for a few hours. when turned it on, the screen was back again. So i used it normally for a few days. it's worth mentioning that during these days i couldn't see initial screens before password entering screen when computer starts . also i found that my webcam wasn't working (i know, alot of problems!). so the reinstalled webcam driver few days later, put in hibernate, start next morning and there was the blank screen again. and it still works on external monitor.

Can anyone give any solution to these problems? Thank you.