“Drinking Up the Pieces,” Unger’s one-man show about these dark days, opens at Theatre Project this week. It’s about the end of a relationship, but not the one you think. “This is not a show about ‘chick breaks guy’s heart,’ because you shouldn’t do that show,” Unger says. “Let Adam Sandler do that movie.” Instead, it’s about the loss of the little boy. He wasn’t Unger’s flesh and blood, but to Unger, he might as well have been. “He was my son,” he says.