Low Oil Pressure light and warning on along with check engine light.

What is your question?

We were traveling and the Low Oil Pressure light/stop engine warning came on along with check engine light. We added oil and drove a couple miles and it came back on and the oil pressure gauge dropped as well. We pulled over and called a mechanic and we were told since the oil levels were fine, there was no oil on the ground and the truck was running fine that it was most likely the oil sensor that was bad. There was no knocking and engine seemed fine. We were out of town and had no trouble other than the horrible dinging for the remainder of the three hour trip. When we got home we had oil pressure sensor replaced. That was two days ago and the third time I drove the car (locally) the oil light came on, followed by the check engine light, then the oil pressure gauge dropped and then the Oil Pressure low warning/stop engine came on and chime began again. Engine seems to be running fine. We had a new transmission put in less than 3 weeks ago. HELP!!!!! Any ideas?