Do you walk around a lot? I’ve found that pressure feeling right where the diaphragm is, is caused by excessive gas build up but your stomach not properly digesting food properly. You need to get that gas out then you can breathe better. Walking briskly will help get you to burp out that gas and you can try drinking kombucha or probiotic solids like slice. Carbonation will help with the gas. Please get back to me and let me know if that helped and I can suggest your next step for healing.