A high-pitched squeal when you brake is usually the wear indicator, a small metal tab designed to make noise when the pads are nearly done. It's not an emergency yet, but it's the last warning before the next one.
Grinding means the pad material is gone and metal is on metal. Every stop is now cutting into the rotor, which turns a pad job into a pad-and-rotor job. If you hear grinding, stop driving it and get it looked at.
A pull to one side under braking often means a sticking caliper or a collapsed brake hose. A pulsing pedal or a steering-wheel shake when slowing down usually means warped or unevenly worn rotors. A soft or sinking pedal can mean air or moisture in the fluid, or a leak, and that one is a stop-driving-now problem.
Winter makes all of this worse. Road salt corrodes caliper slides and brake lines, and ice-covered roads leave no margin for brakes that are already marginal. Have the pads measured before the first snow, and if they need replacing, FixBros will do it in your driveway at 15% off.