I would go under "Battery" in settings toward the end of the day, and see what it says first. You may have an app that you don't realize is using a ton of juice. After the last System update, first Facebook Messenger, and then Facebook itself both started to drain my battery like crazy. I uninstalled, and reinstalled both and the problem went away.
Basically, if anything other than "Android System", "Android OS", or "Screen" are the top users of battery, that app is probably running in the background and needs removed and reinstalled. If this isn't the case, then yes, you may need a new battery.