I'm using a ton of data on my iPhone 5?

I just got the iPhone 5 about a month ago. I used up 2GB (half of my shared data usage) about 2 weeks ago which seems fair considering I wasn't hooked up any Wi-Fi. (I was on vacation.) Anyway, I was hooked up to Wi-Fi for 2 days and went 3 days with LTE and it seems that I used up an additional 25% of my data! That seems ridiculous! I have since connected to Wi-Fi and shut my phone off whenever I'm out. I've looked around and people have said that I need an update that pops up when I go to General>Settings but I haven't seen it. I need something quick and easy.

That seems a little to much… But you can talk to your carrier and try to get a personal hotspot. That is basically a personal Wi-Fi account.

Don't watch movies/clips. They use a lot of bandwidth. Download apps ONLY when connected to Wi-Fi.
There's nothing wrong with your iPhone. It's just your usage.
You can disable cellular usage by going to settings > general > cellular and then turn it off. No need to turn off your phone.

Stay off your phone more!