Question about acceleration problems?

My car is a 1994 plymouth acclaim. My problem I am having is that when I am driving all of a sudden my car starts to slow down and feel like its going to stall (automatic transmisson) and I start pressing on the gas and literally have to push it completely down to the floor to get it to go again and I probably look like a crazy driver slowing down and accelerating suddenly and hard (jerking like). The check engine comes on periodically. I have put a lot of money into this car because I can not afford a new one right now. I have had a new alternator, belts, spark plugs, tune ups, I regularly get oil changes, I even have a new distributer, new fan, fixed the AC and the thing that turns my serpentine belt! I would like to know if someone could give me some input?