From the little you have told us I take it your doctor has told you (confirmed) that you have double heart murmur... and that is is caused by the valve timing you describe. Was this determined with an echocardiogram?
Many people have heart murmur due to imperfect valve operation, and live long and productive lives. At your age it is important that you discuss with your parents and try to resolve you fears. Again, it is my guess that you have nothing to worry about but do have a condition that should be checked on from time to time to see if anything gets worse.
I had a leaky mitral valve, and it may have caused a murmur, but I can't say I was ever so told or worried. My mitral valve over the years digressed to to a point that corrective action was needed. That didn't occur until I was 67 years old... much, much older than you.
I was born with a double heart murmur, which went away as I got older. If cardiomyopathy doesn't run in your family, you are most likely safe. No need to be concerned unless your doctors tells you to be.