Alcohol consumption timeline

Hi there! My wife and I are now expecting (unexpectedly) and I am really worried about our drinking during the time after conception. Does anyone have experience (or even reassurance) on people who consumer alcohol unknowingly in the first month or so of being pregnant? If it was isolated instances of heavier drinking vs regular heavy drinking vs just moderate drinking does this make a significant difference? Is any alcohol bad, or at what point does it become harmful and it what amounts? Sorry, first time going through all this!!