kiora, try a different battery. It is possible that you battery has failed. The other thing you could try is a soft reset first
Press and hold the Power key for 10 seconds to reboot it. Of course you can also simply remove the battery and reinsert it after a few seconds.
If that does not work, try a hard reset (You may lose all of your files, so do not do it if you have no backup).
1 Turn the power off.
2 Press and hold the Power/Lock key and Volume Down key on the back of the phone.
3 Release the Power/Lock Key only when the LG logo is displayed, then immediately press and hold the Power/Lock Key again.
4 Release all keys when the Factory hard reset screen is displayed.
5 Press the Power/Lock Key to continue or either of the Volume Keys to cancel.
6 Press the Power/Lock Key once more to confirm or either of the Volume Keys to cancel.