Before anyone starts criticising your breathing and setting you weird breathing exercises, make sure they have at the least taken a peak flow reading. This is where you puff down a tube and compare the reading with your height, so you can monitor your lung function. There are too many trainers hanging around who attended an online course and are now taping peoples mouths up while exercising with very little assessment of the science behind it.
Make sure they do some basic assessments first. The peak flow meter is one of those basic tests! You may need breathing drills.
This reading is combined with a visual inspection of how you breath ( are your shoulders and chest rising, or do you breath through your abdomen) how many breaths do you take a minute ( or your respiratory rate). Take into account if you breath through your nose or your mouth.
Its worth while pointing out that whilst its arguable the you should breath through your nose. no one has reported an improvement in physical performance due to it. Some metrics do change, but for months of getting used to nose only breathing, I’d want to be able to run faster and/or lift heavier. No report this far has shown this .
Really, get a full assessment first !