Maybe that explains why my battery is draining so fast, even though I’ve shut off some of the activities that use power.
Try doing a force quit cold start by holding the off switch and the home button for ten seconds to shut your device down, then start it normally. That fixes most cases of battery drain.
If that fails, go into settings > General > Reset > Reset All Settings. This will reset all variables without erasing your contents, documents, and pictures. You may have to put in some passwords, and I recommend assuring your backup is current before doing this.
If this doesn’t solve the issue, Apple says to reset EVERYTHING and Restore.