Can bv go away on its own if left untreated?

BV germs reproduce when they feed on the sugar and protein imbedded in vaginal mucus. As long as both are present in the same place they will remain. Random healing might occur or may persist. In medicine we never say never. There are some simple over the counter treatments that many fine useful.

Probably yes, but you cannot rely on it. Best to see a doctor to confirm the diagnosis and get treated.