It's hard to pinpoint your problem without a video so we can see what you're doing wrong. So if you could attach a vid, it would help.

My guess would be you're doing it wrong. This is based on what I see in the gym where newcomers would generally squat with their knees extending over and say they too have balance difficulties. Try sitting back when you squat, push your butt back as if you're going to sit on a chair. There are a lot of youtube vids showing you how to squat, you might want to try there.