I get that same under the left breast pain that you have. My cardio told me it was damage from high BP. I've tried all the medications. Some didn't work, others gave me allergic reactions & the last one (calcium channel blocker) got my BP down to normal but constipated me so much, I went thru misery. I'm done with these medications. I've done research & some can cause death or don't help the real reason pressure is high. After much research, I'm going the natural route: magnesium orotate, African Mango & an herb called Mukta Vati. Look these up. Unfortunately, it's all hit or miss since we are all different. Get a different cardio, tho doctors rely on Meds. It's what they know. You've got to be proactive & help yourself. There's no other way. Oh, and deep breathing 3x a day helps, too.