1997 Pontiac Grand Am White smoke coming through tail pipe

White smoke is engine coolant, vehicle is burning coolant. When you changed the sparkplugs were they very clean, and when you changed the oil was it milky and brown, these engines had alot of lower intake gasket leaks and head gasket failures. If you continue to run the car this way what will happen is the coolant will fill the engine and wash the oil off the cylinder walls and seize the engine, and the vehicle will overheat. This could be a very expensive fix.