1996 Ford F-150 Engine failure

I have a 1996 Ford F150 302 v8; (new battery, new spark plugs, new fuel filter). About 6 weeks ago my truck started having trouble starting like it was starving for fuel, but would eventually start and run good; but on this particular day (6 weeks ago) as I was traveling at a speed of 45 mph on level road the engine completely shutdown and I had no power steering or brakes as I started down hill; I finally got truck to stop before hitting someone or anything. Engine started back up with no problem and I continued on my trip. Two days later I told a mechanic what had happened and left it with him to test. He kept the truck for 5 weeks and said he found nothing but Oxygen sensor was bad and said that would cause the problem I was having. It started for him with no problems as he drove it around. He then called me to pick up truck. I drove it for another week with no problem starting or engine failure. Check engine light came back on so I stopped by Advance Auto to have computer read engine light and results were Oxygen sensor bad and 2 egr codes were also showing. Had Oxygen sensor replaced then, check engine light went out. Next day check engine light came back on; so I called the mechanic and he said to drive it another day to see if check engine finally goes out. It did 2 days later; so I took truck back to him so he could put computer on it and Oxygen sensor showed good and no egr codes showed. Ran like a top for 2 days, then 3rd day doing approx. 35 mph engine completely shut down again as I was driving so mechanic hooked up his diagnostic machine to it and it did not show any bad codes what so ever. It is so dangerous to drive right now but I can't seem to find any mechanic around my area that can fix the problem. PLEASE HELP!