Hello Amet.
I believe you read my post on another thread, so you know we both have this same issue. You already recognize your trouble breathing is a symptom of fear or anxiety and not a medical problem (unless you've yet to talk to a doctor), the evidence being that you are posting on a site such as this, so you are already ahead of the game on this one. I should ask, what specific thoughts do you have when you are focusing on your breathing? For me, I feel that once my mind starts to notice that I am breathing, that there's nothing I can do to take my mind off of it. Another fearful thought of mine is that since I am now too heavily focused on my breathing, that it will throw my natural breathing rhythm off no matter what I do and I will start hyperventilating and panic. A good thing to remember is that you don't always have to have a panic attack when you notice symptoms of anxiety; though it may be hard not to, you experience symptoms like shortness of breath, muscle spasms and sweating when you aren't anxious, such as when you are exercising. You have to remember it is mostly in your head; it is your reaction to the physical symptoms you start to feel that make you panic. You are not in danger when you are hyperventilating or even when you are just simply focused on how you are breathing. I have not yet started my exposure training but I plan on trying to force myself to start hyperventilating every day for a little while to get my body used to how it feels. I know that I won't die or pass out as a result of doing this, my evidence being that I will be totally fine after I do this a few times. Another thing I will try is just to hold my breath for as long as I can before I start to feel uncomfortable, something which I did to cope with anxiety the first time. I hope this helped and let us know how you're doing later on.