Hi, I have had this and it sounds like you might be overbreathing, (hyperventilation.) If it is, indulging it merely increases it. It is real hard work forcing yourself not to do it, and you get in a real mess not feeling relaxed and natural about breathing and you get a sort of ache high up in your chest. Go to the board for breathing disorders as there is a big posting about it!
You should check with your Doctor first to make sure there is no physical problem.
It can be an anxiety disease. I really wish you all the best with this, it CAN be overcome, if that is what you have. i have, more or less overcome it, but I must lurk elsewhere now before I think about it too much! that is one of the ways I tackled it! Distraction