Possible fuel pump??

[04sedonamom]

So, I have a 2004 sedona 3.5 L lx , that I've had for about a year now. I'm now starting to question the fuel pump possibly. When the van gets warmed up, where the termostat is showing normal, I hear like a humming noise, kind of sounds like a honda with a coffee can trying to pass - you know kind of like a dying cow? . Starts from the back and makes its way up front and gets louder and a higher pitch . Happens every once in awhile but several times in a day, I really hear it on the freeway and at idle for a stop light. But like I said it only does it when the van is at normal heat. Starting to get concerned - please help - anyone else have this problem??? I don't want to pay $400 for a new pump.