2004 Dodge Intrepid Radiator

I just had a brand new battery installed. I had a new water pump, new timing belt, and a plastic piece replaced that was attached to the radiator because antifreeze was leaking and white smoke was coming out from under the hood. Less than a week later, I am now smelling coolant and seeing white smoke again! Could it be that the leak is still not fixed or could it be something else? I notice that after driving a while the car will jerk a little, then I can't go more than 45 mph. The engine revs to 3-4 RPMs but the car won't pick up speed. Now I'm wondering if it's the transmission. The engine light is on, too.Help!