Sounds like you may have a bad head gasket allowing oil to mix with the coolant which gets beaten to a froth from the water pump. The cure is to pull the head and replace the gasket. Be sure to fully flush the cooling system to remove all traces of oil. Hopefully the head isn't cracked also. If it is you will be need a new (used) one as they are not repairable to my knowledge.
Good Luck!
Good Luck!