How to tell which app is draining my battery on my iPhone 4s?

I have three email accounts set to retrieve it manually, facebook (push notifications only for wall post, comments and messsages), twitter, instagram (push notifications from only comments and people I follow), tumblr, instafollow, pandora, ebay, amazon, victoria's secret/vs pink, find my iphone (not logged on), craigslist, cinemagram, twitbird, password app, pacsun.craigslist, chrome, textfree, big date lite, angry birds games (for my cousin to play, which was like three months ago). All the apps are not pushed only the ones I said above. I rarely play games on my iPhone; I only use it for social networking and texting and emails and phone calls (rarely talk on the phone though). I've had this phone since Jan. 2012, but the battery seems to be acting up--everytime it says 1% before I plug it on the charger, but after I plug it in, it says 7% or 14%. Sometimes the phone shuts off when it says 5% and sometimes when I pull the tab that says "Tap to tweet" on top, it crashes and reboots itself. Is something wrong with my phone? Should I take it to Apple? I don't have insurance for it.

Added (1). The bluetooth and GPS are always off, and I only turn on my Wi-Fi when I need it. My brightness is set to auto-bright--never above half.

The things that most commonly run the battery down are if you have gps, bluetooth, screen brightness high and skype turned on.

Set your screen to adjust itself on it's environment turn off the rest they constantly run in the background and drain the battery.

You can turn them on when you need them.