Sean,
I can understand your concern over your medical problems. While easier said than done, I would try not to worry too much about all of the different possibilities. Take things one day at time - get the echocardiogram and discuss the results with your physician. You may find that you were worrying about nothing at all.
I have AS and suffer extrerme fatigue as a result of it. I was diagnosed 10years ago , I'm 46 now and its a terrible illness, though it is my understanding that only about 3% of those with AS will develop any heart valve disease, will be interesting to see the doc answer Take care.