As you probably already know, when we are under
stress, our body secrets cortisol, the
stress hormone. With elevated cortisol levels, we are more likely to increase blood pressure and heart rate, increase weight gain, lower immune system, etc.
My best advise it to eat healthy and exercise, so you can help your brain and body to better manage stress, midterms or finals. There are no "magic pills" for any ailment in the world.