Battery is dying really quickly

Iphone 4

ios 8.4

I'm just listening to pandora, or watching twitch, or on social media for a matter for an hour and a half, and i look at my battery life and its in the 40's. It used to be able to last well over 8-10 hours of usage before even being in the 20's. Even when its not being used and just sitting on my desk and not being used and is idle, the battery is draining. It barely lasts 2.5 hours before turning off. Not sure if its the ios or something else. Its not an app, i have push mail and location services turned off like some other websites have said to do, nothing is working.