Why has my eyelid been twitching for a week?

Usually benign: Most common cause for twitching of the eyelids is probably "orbicularis myokymia", essentially a spasm of the eylid muscles for no apparent reason. There may possibly be a connection with stress. If the twitching stops on its own within a few weeks, usually nothing needs to be done about it. A more forceful, and long lasting twitching could be "blepharospasm" and should be evaluated by an eye md.