Something to definately watch for is to make sure your back is not rounding. I squatted like this for a long time. It gave me some extra depth but in the end its not helping you. Make sure you're keep a tight natural arch in your back all the way to the bottom. You should feel squats mainly in your quads and glutes but you will feel it in your back as well. For me it used to be that my quads never got tired first because my back would be so stressed/strained for rounding out and straightening again. It gave me alot of trouble with soreness and really hurt my deadlift progress as well.

Watch some videos and then go do some squats with just a bar in front of a mirror. Standing sideways to the mirror might help too so you can see your back profile better.

IronWorker