Black screen but still working.

Yesterday I woke up to my laptop not displaying anything on the screen. I plugged laptop into an external connection display (being my TV with an HDMI cable) and everything displays fine there. Everything works fine, keyboard, programs, USB, everything.

I noticed my fan works very hard and gets over heatedly easily when too many programs are functioning at once.

If anyone can help me with some suggestions as to what to do, I would greatly appreciate it! Thank you!