You will need to check two things. One is the oil, the color should look normal, if it looks like chocolate milk, you have a head leak, or cracked head. You might also have a leak under the intake, leaking into the plenum. Last but not least check passenger floor board for wetness, might be a bad heater core. Local auto shop can run a pressure test, this will show where it is leaking if it an external leak (i.e. bad head gasket, bad hose, bad pump.)