I hope that someone will come along and reply to you, that can relate to your experience with the chest pain and anxiety. I cannot, because I am 52, and unhealthy. I have had a heart attack, and lots of anxiety in my life. How do you know what a heart attack feels like? It is such a different experience for those that have had one. Some folks have "silent" heart attacks, especially women. Some have the classic symptoms, like I had and is frequently described in the medical literature.
I would like to say that some congenital heart defects do not become apparent until around your age. You have had tests that should have found any abnormalities, but also could have missed something. Regardless of what the test found and the level of your anxiety, you still need to find out what is causing your pain.
Have you ever had pleurisy? It is an inflammation of the outer lining of the lung(s). I have had it, and sometimes the pain is sharp and sometimes dull. Have you had a chest x-ray before? Do you smoke? You might should see an internist, since problems with various organs can cause pain in the left side of the chest.
Be persistent with the doctors untill they find the cause of your pain. Don't let them brush you off because of your age