Nikon D7000 Holding down shutter won't autofocus?

I just bought the Nikon D7000 as my first DSLR camera. I'm extremely new to this and have been reading through the manual/youtubing videos and trying to learn all of it's functions. I'm not sure exactly what I did but now when I hold down the shutter half way it doesn't autofocus. When I hold down the Autofocus button on the left side of the camera and try to move the dial to adjust the settings nothing happens at all whereas before I remember it would change the settings.

Is your lens in the auto focus mode or manual focus mode?

Is the camera in the manual, single or continuous focus mode?

Did you look in your user manual on pages 91, 94 and 96?

208 and 209 will tell you how to set up your camera using the cameras menu

Lens is in the auto focus mode and so is the option on the camera.
I have the settings on manual

On page 92 it talks about holding down the button and moving the command dial. When I do that nothing happens it says that AF-A is supposed to show up on the info screen but it doesn't even show that.

I feel like I accidentally turned the auto focus button off or something but I can't find out how to undo it.

If I go into the settings and turn on the back focus it works through there but I liked it better when it was under the shutter button.

I'd reset the camera as per page 151 of your manual.

A very useful aid to use along with your Owner's Manual is this video:
http://www.nikondigitutor.com/eng/d7000/index.html

Who better than Nikon to produce a video explaining the many functions and features of your Nikon D7000?