When Gaila calls for the lights and asks if Kirk doesn't love her, too, Kirk sits back and says, "No, I meant..." -- correcting her, as though he was meaning something else completely. Then Uhura interrupts them.
He's not talking about what she said.
I've only watched it once, but is there any chance what he's actually reacting to is Uhura returning?
I don't know how big cadet quarters are, but could he have heard someone moving around when he's not expecting it? The Kirk version of spider-sense, I suppose.