2000 Ford Explorer (Fuel Problems)?

So here's the deal, I have a 2000 Ford Explorer Limited 5.0 V8, and I have changed the spark plugs and wires, the fuel filter, just replaced the fuel pump relay fuse and another relay fuse, and the truck will not start, or when it starts it sputters and cuts off, or when started and you push the gas pedal it chokes the fuel off, also whatever it is, its causing my battery to go dead. I have not changed the fuel pump because I talked to a mechanic and he advised that since the truck starts sometimes, that it is not the fuel pump, because the fuel pump goes out at once and does not partially go out. So I'm in a rut I need help ASAP, I'm still paying for the truck, so i definitely want to get it running.