Whatever you are stressed out about, remember its not the end of the world and letting it effect your health such an extreme way is letting the situation control you rather than the other way around.
Talk it out whether its with friends or family, it helps to clear your head, or else try keeping a diary for some time, as long as you have a way of getting your thoughts and anxieties out, you'll feel better. Exercise is another way of beating stress, if you do it enough, you won't have the energy to over-worry about your problems too much.