To expand on this, the posture is really so important, this muscle the iliopsoas connects inner hip to low back on opposite sides, forward head sometimes also has anterior pelvic tilt, anyways your diaphragm is connected to this muscle and if it’s tight, or holding your pelvic in a tilt, it can make the diaphragm not be able to take full breaths. I’ve done some relaxation stretches you can search for this muscle, like laying down with one knee bent and leg up like a square and other leg straight out or slightly elevated, and “dead bug” yoga, and found my breathing suddenly improved on several occasions.