1993 Saturn SL2 Brakes

My brake pads are still fairly new and every time I apply the brakes they make this harsh vibration. I did notice that my rotors are heavly worn and the rubber seal on the back of the calipers are showing wear. But the rubber seal and the rotors have always been that way so why is it only now that its vibrating. And making a wooping noise. It kinda acts likes when a abs braking system applys the brakes and disengages the brakes to prevent wheel lock up during sudden braking, only this year saturn does not have abs