Think im going for a fuel pump soon

[old Rusty C10]

00 2.2 automatic S10 138600 miles No CEL or anything
truck starts up cold real quick ( i have a full tank)
I drive it all over and it starts up fine and as the gas starts going down the truck gets harder to start..more cranking and a couple of times it seemed as tho it had turned over and it didnt so i had to crank it a second time.
Once i get it going it runs like a champ
get to half a tank and the thing starts right up
drive for about 30 or so miles and shut it off and it took a bit to start it..
Im thinking that its prolly junk in the tank or jamming the fuel pump screen?
or is there something i should be looking at on the fuel rail?
Prior to this the truck sat for over a week except to move up and down in the parking spot . Other than that ive had the truck a month and used it a few times without problem. Its got a locking gas cap so i dont think anyone put anything in my tank
Another thing im noticing that when i start the truck the wolt meter reads low and within ten to fifteen seconds comes up to normal around the 14 mark. The oil pressure goes down but if i shut off the truck for even a couple of minutes and then get back in it reads over 30 PSI then goes down once hot to about 15 at idle... I hope its not a major electrical problem in this thing..
anyone have any ideas?