Although it certainly wasn't logical, Spock was unable to keep from finding a small bit of humor in her words. He recognized her attempt at flippancy as a defense mechanism and knew that she was far more worried than she appeared. Yet the knowledge that she'd managed to come up with a literal translation that bordered upon utterly ridiculous yet was in some ways startling accurate, was both comforting as well as amusing.
Still, the humor was short-lived and in its place was a heady mixture of embarrassment, pain, and longing as he forced himself to speak. To explain something that he desperately did not want to even think about, much less speak of.
"It is a time for mating." The words were clipped when he said them and his gaze was not quite able to reach hers. His ears were tinged green and there was an expression upon his face of clear distaste. He turned slightly, unable to put his back to her but also incapable of looking her in the eye. "I am... incapable of controlling myself, currently, Nyota. I am nearing the stage of plak tow. My thoughts, my emotions, are not my own."