Your back is too vertical which is making your knees go too far forward. As you come out of the bottom, you're leading with your chest. Watch your hip angle as you start to come out of the hole. You'll see it opening when it should remain fairly constant until you're almost halfway up. Fix this and this weight is really no problem for you.
Your back angle needs to be more horizontal. A lot more. The first thing you're going to do at the top of the squat as you start to descend is point your nipples at the floor. That will establish a more correct back angle early. As you approach the bottom, you may have to think about pointing your chest at the floor again and reaching back hard with your butt. You will keep your upper back locked in extension as you do this.
As you come up, you'll imagine the weight is attached to your belt and drive up with your butt.