1999 Chevy S-10 oil gauge

When the truck is cold it runs great however once it warms up any time I come to stop I lose oil pressure and my check gages light comes on. This is not a fluke being that it happens every time I drive my truck. I have had numerous feedbacks and would like to hear from someone who knows what it could be instead of guesses as to the problem. Is it the sending unit or the oil pump itself. If it is the oil pump could you tell me where it is located on my truck. And also my fuel pump is staying on for extended periods of time to where I have to actually remove the fuse to shut it off. Any input will be more hen helpful. ~Thanks~