Fuel problems

I have always had problems with the fuel shutting off whenever I fill at the gas pump, but now it is also spitting some of the gas back out. There is also a decrease in fuel mileage and my car gets "hiccups" a lot. When I depress the accelerator, it lags in power at first then jumps way up there before coming back down again. The check engine light is illuminated and I have run a diagnostics code reader on it. I know the catalytic converter is faulty but I am just wondering what else could cause it to perform this way? It did not do this whenever I first got it, so I am not sure what is going on with it. Thinking either fuel pump or fuel injectors. Thanks.