Why is this happening to me?

Cut down on how many classes you are taking a semester so that you can relax and spend more time on each of them. You don't need to be in a hurry to get your bachelors degree. If you are in a hurry you are only learning to pass the class you aren't taking everything in like you should and want to. You have to high of expectations for yourself as well so you are stressing and not focusing on what needs to be done. Learn to meditate or some sort of relaxing techniques.