Hi Kitty i wanted to let you know i get that same feeling and its like you feel like you are going to suffocate to help i do slow breathing exercises.My psychologist gave me some info i'll share it with you.
If breathing becomes unbalanced,as it sometimes does in panic and anxiety,this can lead to other unpleasant symptoms.There may be a slight,non-harmful decrease in oxygen to the brain,giving rise to the symptoms of dizziness, confusion,sense of things not being real,blurred vision and hot flushes.Other symptoms such as a sense of choking, smothering or breathlessness may occur-even though the person is actually getting more oxygen then is needed.Also,because of rapid breathing(particulary if it is shallow)chest pain may occur due to the fatigue of overworked chest muscles.
Hope that helps you.Take care.
Lulu..