Only guest account shows up at start up on Macbook Air

Last night I was updating my Macbook Air, left it alone to do it's update, came back the next morning to turn it on and it was stuck at the apple logo.

After preforming a safe boot, it took me to the login page however only the guest account shows up.

I'm not sure if something went wrong during the update, it was at 70% battery life when i preformed the update so I didn't have it plugged into a power source like recommened, but i've never had a problem with it before.

I've tried enterng control+alt+command+enter which gives me the chance to put in a username and a password.

First I enter my name and passwor, but it was rejected.
So then I tried my apple ID and password, and it was rejected again.

I know I'm entering the right username/password, because it has been the same for my Air, Pro, and iMac.

Now I'm not sure if the account even exsists on my Macbook Air, but the guest account only allowed me to use safari.

I'm not able to access system prefences or anything.

I'm also having trouble with my iMac after updaiting to Mavericks, it work fine until the update and now it's saying my disk is corrupt, but that's a whole other story.

I'm just hoping to fix the problem at home because I really don't want to take two computers down to the Apple store.