Why is my backlight out?

i got a new case the other day and the very next day that i had it on i dropped my phone. i drop my phone all the time without a case and nothing happens but i dropped it with a new case on it and my whole screen shattered. they next day i was watching a movie on my couch and dropped my phone onto the hardwood floor. i picked it up and tried to turn it on and the screen would go from black to navy blue but i cant see anything. my phone is still responsive (vibrates when i plug it in, makes sound or vibrates when i get a text/email) but i cant see anything on the screen. what did i do and how can i fix it?