Help whats wrong with my car?!?!?!?!?

I have a 2003 Dodge Neon.Whenever I start it up it starts sputtering, and then when I get going, when I get to 35 and start going faster, the car will sputter again. once I get past 45 its usually fine. Then when I get to a red light and stop, the car does not want to stay still. If I dont put the brake down hard, the car will lurch forward. What is wrong with my car? Help me please!