To find out what you are stressed out about, you have to take inventory of all your responsibilities and burdens which your have to take care of on a daily basis. In this hyper-competitive world, many of us think we are invincible and able to carry any load with no problem. However, our bodies betray us when we take on more than we can handle, and our bodies rebel by breaking down. So when your body is stressed-out, you have to listen to that and start to take inventory about all your stressors.
You may find that it may not be just one stressor, but a whole bunch of them together that is causing you to be stressed. If it's just one or a whole bunch of stressors, then you have to decide if you will unburden yourself of that stressor, increase your coping skills, or a combination of the prior two choices.
You can start to cope now by instituting some immediate relaxation techniques to get your stress levels lowered now.