I am sorry you are having this pain and also that it is causing your anxiety to spike. Please make an appointment with your Dr. for a medical screening exam to find out what is causing it.
I believe you will feel better after consulting a physician and your fears of dying will be lifted from your mind.
Kitt has given you excellent advice. If you're feeling that badly, you should go to your doctor and see if it's something you need to be worried about or not.
I hope you feel better soon!