Here's a video. Unfortunately it's probably the worst set of the day (last one) but please tell me where I'm going wrong.
Good stuff putting up a vid! It's really not that bad but fortunately for you I have several tips that will help:
1 - Get some shoes. Any shoe with a solid base will do. Support for the arch is even better. Spongy trainers do not give support and going bare foot can flatten arches. A strong sturdy platform will allow you to balance better. You will note second rep you were losing balance.
2 - Depth. This is really personal preference but I don't believe it is necessary to go that low. Below parallel is the aim to ensure good knee health. Going lower hasn't been proven to give any more growth either. This is the target:
Just below parallel is easiest to gauge when the hip crease (ie. where your underpants sit on your upper thigh) is just a touch below the top of your knee, as in the pic above.
You will note at the lowest point your lower back rounds and the hips sort of 'go under' you. This is not good. You want to sit back into the squat as if you were sitting back on the toilet. Not going so low will limit how much 'butt wink' occurs.
3) Stance. Again personal preference but I would recommend a slightly wider stance. Not a massive amount maybe another 2-3 inches so heels are directly in line with outer shoulders. This will help with the butt-wink mentioned above and will also assist in the following point:
4) Keep chest up and back straight. Big breath will help keep this area solid. Hard to tell how you grip but once I narrowed my grip to just a few inches from my shoulder either side it helped to keep my chest up and to squeeze back muscles to keep tight. Focusing on a dot just above the horizon will also help.
That's all I have for ya bud! I'm no expert but I spent a lot of time trying to get mine just right. Hopefully these tips help you.