[SLIP STREAM SVT]

sorry for the newbie question but how do you know if your brake pads are going or gone without looking at it? i never really had a squeal to my brakes before, but now they squeal everytime i hit the brakes, but only if i press them normally to lightly, if i hit it hard there is no sound at all, also i've had my car for almost 2 years now and been to 1 track day, i feel i use the brakes "sorta" hard during street driving, but they still seem to stop really well.