Why won't my phone stay on?

I dropped my phone on the ground accidentally and it would not turn on at first. After I got home I plugged it in and it began turning on, saying it was charging, then flash off. It is stuck in a loop of doing this. If I hold down the power button it turns on then imediately turns off. I can't access the recovery mode or the reset mode because the screen turns off after it gives me the option to select recovery or reset. Can anyone help?