If the oil was severely over-filled you would not have been driving the car for a month. It is more likely a cylinder head gasket is leaking coolant into the oil. Antifreeze will melt the first layer of the very soft engine bearings but that takes time to occur. If the coolant level is low, get the oil drained right away to get that coolant out of the oil system, then have a pressure test done. To be as bad as you described it I would expect to see the oil level go up very quickly again during that pressure test.
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Friday, September 6th, 2013 AT 8:35 PM