Scared with upper tummy is tender and hard to breathe

Hi everyone, new here, I am finding it hard to breathe, upper tummy is very tender and when I breathe in and out it hurts thats my tummy, chest and breasts. My chest is burning badly even though I am on tablets for it and taken gaviscon. I am worried that it could be my heart as have chest pains too and have a minor heart block. Went to A/E the other day, they did an x-ray, blood tests and said it was an ucler, but couldn't say for sure. They thought it was a problem with my heart at first as ecg showed up a kind of block but after blood tests they said its just an minor block that alot of people have, they tested the heart muscles and they seemed fine he said. Now I am worried it could be a problem with my heart as my sister died of a tumor in the heart and they never knew what was wrong with her until she died, they even did a heart scan for god sake. My breathing is getting worse and the burning is killing me. I looked into heart problems, I know I shouldn't of done but if they can't help me I thought I could. I have the same syptoms as some heart problems. What should I do I am so scared. I don't want to die, I have three children, my youngest is only 16 months. I am at a lose end as keep going to Dr's and A/E but no one will help!