I am a 18 year old college student, and I work 40 hours a week, with a fairly heavy pre-medical course load. I am in my 2nd year of college, and have never experienced any chronic stress before, but lately I have noticed many arbitrary symptoms, some of which could be serious. I have had severe stomach cramps, migrains (which I've never had before), weight loss, vomiting, and even rectal bleeding. Could all of this be caused by stress, or is there a more serious underlying problem? I've never had any reason to go to a doctor before, I'm perfectly healthy, I'm a vegetarian, get plenty of exercise, and I don't smoke or drink. What could be causing this?