iPhone 5c battery problems

I Currently have an iphone 5c with a few battery problems the phone is around 16 months old and battery drains a lot quicker than it used to before and now it doesn't last as long from a full charge even tho my brightness is low 3G/4G off , Bluetooth off background app refresh is also off & apps are always closed , wifi also off when ever dont need it has been like this for a while now and also it will sometimes not charge or will take ages to charge and drain very quickly!