HELP ME. My phone battery is an absolute JOKE.

My iPhone 5 battery is absolutely awful, it didn't even last 2 hours, from 100% to 10%, and I was hardly using my phone! It dies at 10% sometimes even 15%! I've got iOS 7, the brightness was the lowest and I've turned many things off to save power. N o t h i n g works. I'm getting very very VERY angry!!!!! I can't go anywhere without my phone dieing instantly, even when I hardly use it. I close all the apps all the time and I've turned off all things like Bluetooth, and the background refresh thing, but honestly nothing works. Is it just my phone? Do I need a new one or is there something else I'm missing here?

Please help me, I'm getting very frustraited!!