so when i pull up to a red light or just stop, my break pedle will be furm at frist the about 20 to 15 seconds later it will start to get really soft, or even to a point here it feels like i'm not pushing it in... my car will start to roll alittle. then if i let it out then press it back in it will so the same thing again... what can it be? rep for anyone that can help