Yeah the anxiety and asthma is very confusing because they both cause extreme breathing difficulties.
I do very much pay too much attention to my breathing and of course I make myself believe that I'm going to die from not getting enough air in my lungs....
I found out that I have an ulcer located in my stomach and it's causing severe indigestion, which causes problems with my lungs. So that could be a trigger also.
When you have breathing problems did you try to put a heating pad on your chest, it really helps for me.
Also, I found out that blowing up a ballon twice a day helps with asthma and deep breathing because it exercises your diaphragm.
I do have to keep myself busy because like you when I'm not doing anything I start thinking about my health and how I could die from these possible diseases and so forth....