I recommend that you speak with your doctor
about your concern. Yes, this is common to some degree for many different people. The GI tract is carefully regulated by a very complex system of nerves that is nearly as complex (more so in the mind of some people) as the human brain and is vital to make sure that all food is digested properly. Having some GI distress during stressful situations, and there are plenty of jokes about this in common usage that you might have come across during your life. As you have experienced, loose stools can be a common finding before a stressful event. In the worst cases, this can result in some nausea and vomiting
. One of the involved nerves is the vagus nerve, which starts in the base of the skull and then runs down to involve the heart and also the GI tract. It is very sensitive to emotions and stress. If you are having difficulties beyond the norm, there may be something else at play that is exacerbating this somewhat normal response. Speaking with your doctor can help, as he or she will be able to ask more questions and determine if you are having normal findings, or if more testing is needed. Again, please speak with your doctor.