I have a very similar situation and I insisted to my doctor that we do a test for MALS. There are a couple of ways to start. One is a very specific ultrasound where they have you breathe out while checking your velocities (if there is a compression of the celiac artery, they will see it with the exhalation). Other tests might include a CTA with contrast. My tests came back positive for MALS and I am seeing a vascular surgeon this week. In the meantime, my understanding is that the breathing, and in my case, heart palpitations (and slow digestion, and possibly even malnutrition), are stemming from the fact that I have a very sensitive autonomic nervous system and the nerves between the celiac artery and the ligament that is compressing it, are irritated themselves and are irritating my autonomic nervous system (causing all of those other issues). A good cardiologist, or even your PCP could explain the autonomic nervous system far better than I, but I hope I have given you something to go on.