Shutting off, seems to be not getting fuel pressure

Hello all. A couple months ago, it would shut off when I was driving. I thought it might have been the battery or something at first. Long story short, I was not getting fuel pressure. I would try to start and it would just crank and crank, no start. Once it seemed to build pressure again, it would start. The distances it would drive before cutting off seemed to have gotten shorter.

What I have done to the vehicle so far to try and fix the problem:

First, I replaced the fuel filter. Then, I replaced the fuel pump. I figured if it wasn't getting enough pressure, that had to be it. Nope! Then I checked the fuse for the relay switch. I believe I checked the right one in the relay center. It is the yellow 40a that says it's for the fuel relay. Then I read that the oil pressure switch takes over for power to the fuel pump after the car is running. I had extremely low oil. So, I put in 3 quarts and tried again. Still shutting off.

I honestly don't know what it could be. I was thinking maybe an electrical problem, but I don't know. I hope not. It's an old enough model to need to be hooked to the older style computer I am told. I don't have much money. My family is on limited income and I am a broke college student. Any advice would be more than helpful!

The car will run for a little bit before it eventually shuts off again. Seems to be 5-10 minutes max!