Constant need to take a deep breath

I'm 16 years old and slightly overweight. I have been having trouble with taking breaths. Last April I got whooping cough, I went to the doctors quite a few times and they didn't know what was wrong with me but I had crackles in my lungs so they gave me antibiotics and a steroid inhaler and reliever inhaler to see if it helped. I also had a full MOT blood test and they checked for everything but it was all normal. What didn't help was that I went on two D of E expeditions and I felt really ill. Even though I did manage to finish it, I felt so ill when I came home and then I realised it was a very bad idea. I got over the bouts of coughing and not being able to breathe however now I get palpitations sometimes and the need for a deep breath most of the time. I am coming into the busy exam period and I am stressed however it started well before the exams so I don't think it is stress related. I feel tired most of the time and when I had a peak flow test it was 360 but it should be around 480. I'm quite worried and need to know if it is serious. Please help!! Thanks

[Jerry_NJ]

I'm an old guy so my experience may not relate well.  

You say slightly overweight... that's how I would describe myself, add to that my age, my overweight translates to belly fat.  I think I notice some breathing impact when my stomach gets large - here I am no more than 25 pounds overweight and almost 6' 6" tall, and I think the fat is noticeable on more than my belt and trousers.

I also suffer from chronic nasal congestion, and that makes me feel like an onset of suffocation at times especially when lying in bed on my back - so I take deep breaths through my mouth and it sometimes doesn't completely solve the problem.  Can you breath freely through your nose?  This is how we are "designed" to breath, mouth breathing is a safety path for breathing, not the primary path.