Panic. He was panicking.

Childe's limbs were barely under his control, but he could feel the bed shifting next to him. His heart was beating out of his chest, his head feeling light all of a sudden. Why were you leaving? Had he not been good for you, to you? He'd done everything you wanted him to so why were you leaving? Had he done something wrong? If so, he had to apologize. He had to tell you he was sorry, had to be good for you.

Because that's how he gets you to stay; by being good.