2001 Chevy Silverado Oil Pump

I recently had the oil changed in my vehicle. I probably let too much time go between oil changes. At one point, my truck wouldn't start, but when I put a quart of oil in it, it started right up. The oil change took place about two weeks ago. When I tried to start it this morning, it wouldn't turn over. I drove it yesterday and it ran fine. I did notice the "service engine soon" light come on about three days ago. Any idea what the problem might be?