The bar is rolling up on you. This is probably being caused by you lifting your elbows at the bottom of the squat, which is rounding your upper back. Keep your elbows lower. Your squats are a bit troubled overall. Depth is lacking, you are not really coming out of the bottom very well, and your knees are coming in. Take 20 pounds off the bar. Get consistently deep. Keep your elbows down, especially on the ascent. Keep your chin down and drive your ass up. For your arm pain, elbows lower may help. If not play with grip width. Try wrapping your thumbs around the bar. If none of that is helping, move to high bar until your arm calms down.