All you should be feeling is the pressure in your core from getting tight and holding your air.
You should focus on driving your ass back, holding your arch, and thrusting your hips forward.
If you 'feel' those things that's really all you need to worry about.
And I agree with what was said about not feeling individual muscle groups on heavy barbell lifts. These are the definition of integration...you cannot lift well if you don't integrate as many muscles into the lift as possible, so I don't see much use in trying to isolate anything with a bar on your back.