Like John said, you need to get a true reading on that oil pressure before you drive it anymore. Driving it with critically low Oil Pressure will destroy that engine quickly. You may not have low pressure at all, you could simply have a defective pressure switch or the wire has come off of it and is grounding out on the chassis. If the sensor is good you have to start looking at possible culprits. Low oil pressure can be caused by anything from a stuck oil pressure relief valve (best scenario) to a completely sludge clogged oil passage or pickup screen (worst scenario).