1999 Other Jeep Models Oil Pressure

I've been using your site to try to figure out my problem, and I was wondering if oil pressure senders and oil pressure sensors are the same thing? My Jeep Grand Cherokee started with 0 oil pressure when idling, my check gauges light came on, and when I accelerated the gauge went back up to between 30 and 40, and the light went off. I changed my oil that night thinking that the filter was bad since I was past my scheduled oil change. Now my pressure is fine when I start the jeep and the more my engine heats up the lower my oil pressure gauge got. It would still go back up when accelerating, but on the way home from work it just went to complete 0 oil pressure all the time. Once or twice I would accelerate, and the light would go off, but the gauge stayed at 0, then the light would come right back on. My oil level is still normal, I just don't know what else I can do. And I wanted to make sure that since my gauge was reading 0 or low, how am I to know that I am not at danger for blowing my engine? It seems to run fine and sounds normal when driving. Thanks