You would know if you had zero oil pressure, by now. Something would have self destructed.

As far as testing, a mechanical gauge is the way to go. You have to screw it into an oil galley, but it will give you the actual oil pressure better than the resistor driven electric gauge.

The stock gauge is a glorified idiot light, anyway. It is driven by a resistor, so it just gives you relative values and in general it reads in three ranges. Low, normal and high. The needle swings according the resistance at the sender, but it does not really give you a solid accurate reading of pressure.

Good Luck,
Michael