Ive had an almost imperceptible constant twitch in my left cheek for five days now and im starting to get worried.

No worries: Isolated muscle twitches are common. They are often caused by stress, fatigue or muscle exertion. They often go away with rest and time. Usually twitches of one muscle are not a sign of a serious medical problem. If you develop tremors, other twitches, weakness or coordination problems, see a a doctor. More info: http://www.popsci.com/science/article/2013-02/fyi-why-wont-muscle-stop-twitching