2008 Chevrolet Impala Battery dying

About 1 week ago, battery died, got a boost, fine for a day, died overnight, boost again checked and cleaned batter cables, checked alternator, checked battery all fine, left cables off battery overnight to see if battery would die, batter fine next day, attached cables all night again battery died. Used tool that checks for shorts as soon as I put tool on negative cable and post light came on which indicates short, removed all fuses one at a time and all relay switches one at a time but light remained on? Light indicates short but by removing fuses still did not say where. Any suggestions guys, Thank you