I don't know if stress and anxiety are causing my breathing problems or if its the other way around. how do i find out once and for all? this is awful

Excellent question: Very related. Learn/practice rhythmic (steady) & diagphragmatic breathing coupled with self-calming strategies. The anxiety & stress reduction workbook by mckay et al can help either way. A medical evaluation may identify treatable causes. A mental health evaluation may identify treatable causes. Stabilize daily living habits (sleep, diet, exercise, etc.) wishing you well in your search for relief.

Look for triggers.: Try to look for triggers or precipitants to your anxiety and breathing changes. A quick session with a psychiatrist will be able to clarify if you have panic attacks or other forms of anxiety manifesting with physical symptoms.