Fanfic / The Boy Who Died A Lot

Harry’s always been known as The Boy Who Lived. Only Severus knows that this is a lie. After Harry Potter dies in his first year during his detention in the Forbidden Forest, Severus Snape is given the time-turner to prevent his death. But messing with time and death has its price and the universe seeks to correct it. In the meanwhile Snape has deal with Harry's adventures and somehow keep him alive.

Found here and here.