Same here, partly asthma, partly poor technique.

I still practice using an incentive spirometer from my last hospitalization. My first breaths are usually feeble. After a few tries it improves.

Regarding breathing from the diaphragm, that technique was apparent from watching Emma Pooley on GCN videos. I could actually see her abdomen expanding and contracting during hill climbs.

Reminded me how bad my technique is and how to help correct it. I tend to tense up when I begin breathing hard, which makes it worse. Gotta remind myself to relax and breathe from the diaphragm.