Brake pedal and car slight vibrates when pressed

When the brake pedal is pressed. You can feel the whole car shudder. Not violently. But enough to notice it. You can feel it in the pedal too. Ive replaced both rotors. The right rotor twice! The right caliper froze up twice which wore the brake pads on the right down to nothing and grinded the rotor. So I replaced all the components. The first time I had replaced it I replaced the brake hose. I belive the back right drum is rubbing on a brake. Maybe its warped or something odd inside. But I dont know if it would cause it to vibrate and shudder. It happens more when you brake at a higher speed. Maybe 45 and higher. You dont feel it braking much at a slower speed. Any ideas on what it could be, or suggestions what to look at I havent already. I greatly appreciate it.