too things come to mind kimw,, either you sending unit is sending false signals or you oil pump is going bad,, when it looses the oil pressur does the car start clattering in the engine,, lifter noise. if so its not your oil sending unit..
oil pressure,, comes from the oil pump,, when the engine turns the oil pump pumps if its going bad its not going to pump.. if its your sending unit going bad then it could be a false reading on your gauge hope for that...