IF... your lower back has "no feel" to it.
IT's like...how should I say, your lower back has lost a feel to it, like you can't contract it when you want to, it's fatigue. When this comes, take a break.

Another method I like to use to squat is;

1. Lower myself and totally squeeze the crap of my legs while I'm moving downwards.
2. Imagine myself pulling the barbell downwards instead of letting gravity push me downwards. I must control the bar.
3. At the lowest point, use all that tension and "jump" upwards. Just powerfully explode upwards

The sticking point is where your body is working against the most uncomfortable positions against gravity. Thus a powerful explosive movement is required to break against this "point". Some people call it cheating, I call it, cleverly manipulating disadvantageous positions for your own good. Weightlifters use this method very often, and my coach does a 265KG back squat at 69KG bodyweight. Pyros Dimas does a 330KG back squat at 85KG with that method.

If anybody calls that cheating, tell that to my coach.

Or another method you can do is after your training, add single limb leg work. Pistols, lunges, bulgarian squats......these work well. About 4-5 sets of 10-15 reps should be good.