You have a major seal or gasket leak somewhere. Is there a pool of oil beneath the car? Best way to find this out is take to a shop and tell them you need a dye test for a major oil leak. This will show any exterior seal leaks and interior when they open it up. Are you losing coolant as well? Do you have a lot of exhaust smoke? Then it would probably be a head gasket. Need more info. but your best course of action is to see a service shop before components start burning up for lack of oil.