Engine oil level

My engine oil light came on the other day. I checked my dipstick and it was on minimum or one quart low. I put a quart in and filled it up to the maximum level. I then drove about one hundred miles and the oil light came on again. I pulled over and checked the oil and it was a quart low again. I put a quart in and filled it up and drove home which was about one hundred miles. I then checked the dipstick and it still registered full. The next day I drove about five miles in town and went home. I then checked the oil it was down about a half a quart. There is no smoke of any color coming out of tailpipe. The car does not miss or run bad. There is no water in the oil or oil in the water. I do not believe this model has a PCV valve. I change my oil and filter about every 3,000 miles and I have never experienced this before. I am at a loss at what could be causing this. Any assistance you can give to help diagnose this would be very much appreciated.

Daryl W.