About a two years ago, this was my first, and triggering symptom of anxiety. I was lying in bed one night, and I had eaten a huge bowl of popcorn earlier that night. I was laying there and suddenly I felt short of breath. I knew that after eating a lot Id feel stuffed and everything, so I went to the bathroom to try and clear my nose if it wasn't because of bloating. It didnt work. I panicked. I went downstairs and watched tv to try and get that feeling to pass but then I suddenly got extremely weak . I went to sleep in fear. For about four months, I looked up health problems related to it and it made me worry more. My mind started to drift away from those terrible thoughts. I was finally okay, and then in January of 05, it hit me again. Hard. I went to three pulminary doctors and they all said I was fine. I felt like I was dying and like I seriously couldnt breathe. One thing I noticed was the urge to regulate my own breathing. I couldn't sleep for quite sometime because when I felt myself dose off Id jolt because I thought I wasn't breathing. It went away for an entire year, maybe a little more. Then it came back just recently, but in small doses because I've...in a way...learned to control it. I noticed that yawning seems to give me a feeling of "fresh air in the lungs". This is a common symptom anxiety from what I've read and been told. This also triggers other terrifying thoughts and feeling of worry. In your case, Im going to guess that it's all in your head, because in a way you are most likely expecting something to be wrong, therefore creating the symptom. Youll be fine, hang in there. Also, theres a method called 7/11 breathing where you breath into a paper bag and almost 90% of the time will keep you relaxed. I cannot remember what the way to do it is, so google it and you should get good results.