Bad rear Brakes or Bad rear Wheel Bearing

I recently replaced both front wheel bearing, drive shaft, radiator, heating core, all ball joints, idler arm and over a year ago replaced the engine due to 3 blown cylinders. So now my rear driver side tire squeaks while driving. At first it would cut in and out during a drive but now its constant. But today when I put on my brakes and heard grinding. Very similar to front wheel bearing sound but its not humming like the front did. So I'm cubit decide whether its my brakes or wheel bearing. I've done so much with this thing I don't want to do one thing and have it be the other. How to know the different signs of either or. Thank you so much.