I've developed an odd chin spasm. it's worse when i am nervous. it starts to happen frequently, especially when i'm having a conversation. what is it?

A Tricky Twitch: Twitches like that (called "ticks," or "twitches," or "myoclonus") are usually, as you guessed, due to stress, pain or tension. They usually go away. Rarely do they progress. They are difficult to get rid of, short of getting your head together (meditation, biofeedback,etc). Drugs rarely needed (although frequently desired). If it lasts more than a month or so, I'd suggest seeing a neurologist