2002 Saturn SL2 Burning off oil every couple weeks

For the past several months I've been replacing my oil every couple of weeks. My low oil pressure alert will come on, I check the oil level, see that's it's nearly empty, so I add oil. Then two weeks later, I get the same low oil pressure alert, find that it's nearly dry and do it all over again. I've been doing this for a good 3-4 months and I seem to need a fresh infusion of oil at almost exactly the two week mark. Yet, I find no oil stains anywhere where I park, so I don't seem to have an oil leak. Yet, the oil is obviously going somewhere.