From the sounds of it... You have the same perdiciment I was this time last year is the engine running rough as well or just sounds like a boxer motor? If it sounds like a boxer motor check the mufflers to see if you haven't blown then baffles out of them or have damaged your exhaust system.
If it's the engine, get the engine compression tested to see if the head gasket has failed between 2 cylinders. If it hasn't have a look at the oil to see if water is getting into it and if that fails, look at the radiator overflow bottle... From the sounds of it, you got a blown head gasket.