nephari

I have a 1999 Ford Explorer Eddie Bauer 5.0L V8. I have had a recent problem develop which included at first, rough idle, hesitation at highway speeds on acceleration and steep upgrades on the road and highway. Originally gas mileage was 16.3 MPG then began to degrade to 13.9, then 11.9, then 10.0 MPG. Now the vehicle stalls at idle and is hard to start. Today I tried to start it then nothing. I changed the fuel filter and still won't start. I have not checked the fuel pressure as of yet. I turn on the ignition to check for fuel pump operation and it operates for 2 or 3 seconds each time I turn on the ignition key. However, when I depress the valve where fuel pressure is taken it does not seem to have any pressure coming from it. Any ideas?