No period for 11 mths

Amenorrhea (lack of a period) can be caused by a great many things. It could be a thyroid issue, lack of body weight, certain birth control drug side effects, ovarian cysts, fibroids, a whole host of things. It could be simple, it could be complicated. Time to see your gynecologist as soon as you can, and have them diagnose you. Tell them about what's going on and anything (even taking vitamins) that might be unusual for you.