My screen is black but ipad is on

If iPad isn’t responding, do one of the following:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

Note: If iPad still doesn’t turn on, or if it gets stuck during start up, see the Apple Support article If your iPhone, iPad, or iPod touch won’t turn on or is frozen.

See the section "If your screen is black". If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support If that does not help, then use the Get Support link at the top right of the page here.

Given your description, you are going to need help. You would be best advised to take your iPad along to the Genius Bar at your local Apple Store - where the technicians will be able to test and assess your iPad. The results of the test will inform your next steps.

Genius Bar Reservation and Apple Support Options - Apple (UK)