Tis problem has been happening to my Tercel for a while now, but this morning it worried me even more, when I was reversing I pressed on the brake, but the car kept rolling back (it scared me) so I let go and press on them again and it was okay, the real problem is when I come to press on the brakes, I had to press farther down then normal, what could this be? And I have recently changed the brake pads and rotos...