Should I be worried about COPD? What could possibly be wrong?

[italianlifter]

I am a 22 year old male who has been having abnormal breathing patterns lately. For the past 3 years all my I would care about was fitness and staying healthy cause I'm the person who likes to take care of themselves and stay as healthy as possible. Never been a smoker and never tried smoking. I have been around second hand smoke as a child but I do not believe as much that it would do damage. I am currently a 1 year firefighter who has never been in any fires and really hasn't inhaled anything that would damage my lungs unless you consider starting up chainsaws, K-12, Generators and Hydraulic Power units. Basically ever since I been having these abnormal breathing problems I decided to run a series consisting of a pulmonary function test, X-Ray of my lungs, Blood test and Pulse Ox. Yesterday when I went over the results with my pulmonologist hen explained to me that everything was normal and there was no signs of COPD or really any disease. He says maybe asthma but didn't wanna diagnose with it cause it wasn't a lot of evidence from the test to show it. The X-ray of my lungs came out clear and normal and the blood tests where normal as well. My pulse ox usually ranges from 96-100 but the doctor said that is normal as well. I do have a cough but i am not coughing up any phlegm or blood. Its just a dry cough throughout the day and thats why the pulmonologist diagnosed me acute bronchitis. He also listened to my lungs multiple times and said to me that they are clear and there is nothing to be worried about. I have also had an EKG done on my heart which came out normal as well. I have never had any anxiety issue. I am still capable of working out but Its not comfortable as i do have to take deep breaths. Basically I don't wanna say that it feels like shortness of breath but i always have a constant urge to take a deep breath and sometimes I am able to achieve the deep breath and majority of the the time I am unable too and I cannot figure out why. I cannot understand why this is happening to me and it is honestly freaking me out and giving me so much stress. I am not sure if I should get a CT Scan to really go deeper into the the problem. The doctor said to come back and visit him in a month once I finish the medications to see if the cough is still present or not and then if it is he wants to put me to sleep and use a tube down my throat to check my lungs. Kinda freaks me out cause I am only 22 years old and I can't understand why this is happening to me. Can anyone please give me some advice and feedback? Thanks everyone and stay blessed. Apologize in advance for the long question and please don't be afraid to ask me questions cause I could of possibly left something out. Thanks! -