2000 Ford F-150 oil pump

To start, like any normal person, I check my oil on a regular basis. One day on my way to work I heard a slight tap from the motor. I thought maybe I did my mileage wrong and that I was overdue for an oil change. When I left work that day, the truck barely turned over, I got it started and got on my way home. When I hit the highway and high RPM's, it was knocking again. But now the knock is much more pronounced. I had to stop on the way home to pick up food, when I parked it the oil pressure gauge dropped completely and the truck stalled. After that it didn't want to start. I finally got it started and drove it home (I just hope I didn't do any further damage) and everytime I came to a stop the oil pressure gauge would drop again. I changed the oil and everything and it's still knocking and jerks as I drive. Someone told me that it could be my oil pump. Is that true?