Sorry to hear about the heart murmurs and the possibilty that you can't join the Navy, but I would take Terry's advice. Heart murmurs can be transient.
I would also advise that you take it seriously though. I lost one of my college buddies to an undiscovered heart murmur/issue. He played college basketball and was extremely active. Then one day, playing pick-up, two years after college, he died on the basketball court. Extremely sad story, and he never had any signs or symptoms.