I had a heart murmur when i was younger however the pain in my chest hurts on the left side and in my back on the left size i havent been coughing

Chest pain: If the discomfort is sharp, fleeting and brought on with a deep breath or twisting motions of the rib cage, it could be due to a pinched intercostal nerve or muscle which runs between 2 ribs. This usually resolves on its own after a few days, but it pains persist, see your physician for evaluation. In the meantime avoid stressing or straining activities on your rib cage. I doubt a cardiac cause.