You could breath that way until you were 80 plus and it would not kill you. It is uncomfortable but not dangerous. I use to have patients that would feel like this when I had them breath deep to listen to their lungs. It's an anxiety symptom and an annoying one. Check your diaphragm to see if it's moving when you breath in and out, if its barely moving but your chest is rising up and down with your breathing than you are chest breathing and causing the feeling. The more you struggle the more you will feel that way, but as stated not a dangerous thing. Hope it passes soon.