96 Dodge Gr. Caravan. Jerking when driving, what is the problem?

[?LISA?]

Ok, this is hard to explain, but here goes. While driving my van today on the expressway, it started jerking slightly, sort of like it was running out of gas, but I have 3/4 of a tank. it got worse as I was nearing my destination. After turning off the van and then turning it back on after about an hour, it drove Fine for about 10 minutes, then started jerking gain. it never quit, but acted like it wanted to. As I was pulling into my road, it was really bad and didn't seem to want to accelerate. I parked it and had my son take it to Autozone to read the codes (the check engine light is on). he told me that the scanner could not read the codes and the employee told him it may be the ECM. I thought that as long as the van is cranking and running the ECM is fine. I will be taking it to another Autozone tomorrow in case their scanner was bad, but can anyone give me any idea as to what the problem might be. We have done a lot of work on the van recently, new fuel pump, crankshaft sensor, ignition coil, water pump, radiator, all new spark plug wires (we did not change the spark plugs though because we had just changed them a few months ago). Also the intake gaskets and valve cover gaskets were changed. Sorry so long and if more info is needed, let me know. Oh, the van is a 3.0 V6.