You likely just have too many things running in the background.
Things like Facebook and games are massive power and memory hogs that run 24 hours a day and will drain your battery quickly.
Install a cleaner app like “CCleaner” to make it easy and fast to kill all the power robbing apps for a few hours or at least until the next time you use them.
You can also go into each apps settings and disallow running in the background
Maybe. Maybe not. You didn’t say whether or not you were using it the whole time.