IPhone 4S battery draining so quick?

My iPhone battery is messing up. I always close my applications after using them and my i can't turn the Wi-Fi on my phone on so the Wi-Fi isn't the problem and the only thing tht uses my location is the weather. But an example of today what happened: I charged it at %100 at like 6:50 and at 7:20 it was done and I wasn't using my phone but I was texting but I'd close the app afterwards by the time it was 10 it was at %20 but I wasn't even using it oh and my brightness is on auto. Can anybody give me suggestions on what I can do to solve this problem?

It might not be your phone at all,
it can be your charger thats malfunctioning & doesn't charge your iphone as it should.

Maybe try charging it with a different charger & see if lasts longer, if it still does the same thing then it might be your iphone the one thats malfunctioning, ?