I have these all the time the tummy thing you are feeling will be trapped wind because when you panic you swallow air and it causes the uncomfortable feeling. Tell the anxiety to go away tell it its not real its just a thought. Try and breathe slowly concentrating on inhaling the good air and exhaling the waste. Say it to yourself as your doing it. Also as mad as it sounds try and do something right brained like singing. You will focus on remebering the lyrics and it will pass. Once you relax and the air releases you will feel better