Help 94 won't stay running

[DU516]

I just recently bought a 94 2500 it 0nly had 48,000 miles on it when I bought it .In the last month I've changed, the oil, and fuel filter . new starter ,and put a brake switch in because my brake lights wouldn't go out plus the cruise control didn't work. Now yesterday when I was driving it just shut off the whole truck started shaking I pulled over to the shoulder it stared back up fine then a couple of miles later it did it again this time it was harder to start. So It did the same thing a few more times on the way home. When I got home I let it sit in my driveway for about 15 minutes runnning never shut down. I then drove to my buddies shop to put it on the lift to check things out. When I got there I shut it off for about 20 minutes, it restarted fine then put it in reverse it died and would not start it took several tries then finally it started but I had to keep reving it to keep it going. We checked around to see if any thing was loose and found nothing
I drained a little bit from the fuel filter to see if I had any water but nothing. We didn't find anything but the truck is getting even harder to start and when I drove home it still just keeps shutting down. PLease HELP.