I've been feeling very anxious and can't sleep. what could cause me to feel so anxious?

May be diet: Strange as it may seem a diet with empty calories, particularly sweet stuff, will alter the chemistry in brain so that your emotions are more easily initiated.

Depends: There are many types of anxiety, many of which can be related to life changes or stress in ones environment. Anxiety can also be related to our physical health or the use of various substances. Sometimes however anxiety comes out of the blue, without apparent reason. Your family physician would be a good place to start in trying to understand why you're experiencing so much anxiety.