Because there are soooo many reasons why you feel as though you can't get enough air, there is virtually no way that we can offer advice on how to control it. Since it usually happens in the situations that you listed, which increases your stress levels, have you given any thought to checking to see if you may have a touch of asthma? What you describe sound so much like what my son experiences with his asthma.
I do hope that you find an answer, and a way to treat/control this. Please speak to your doctor and then let us know what you and he decide.
Peace and Blessings
Look For The Good and Praise It!