Welcome to the forum!
I'm glad that you found it and that it has helped you to calm down. The good news is that you have a doctor who sent you for an ultrasound to investigate your murmur and they found the cause.
You might not ever need surgery, it could be years away if you do need it, or it might be just months away. The important thing is that your valve condition is now known and your medical team can monitor it so that you can get surgery to take care of it in a timely manner, if and when that day every comes.
Aortic stenosis is a narrowing of your aortic valve, usually caused by calcification that has built up over the years on the leaflets of the valve. If you are interested about how the severity is determined you many find the link below helpful. If you look at Table 1 you will see the three most common metrics used to determine aortic stenosis severity, valve area (AVA), peak velocity and mean pressure gradient.
When I was first diagnosed with aortic stenosis, the severity was classified as moderate, and all three of these metrics agreed, falling into the moderate range from Table 1, as determined by my echo. Echos were completed regularly after that to monitor the progress of the stenosis and 12 months out from my original diagnosis, one of the 3 metrics, pressure gradient, had crossed the line into the severe category. The other two metrics were still on the moderate side of the line, but just barely. At this point, I was classified as moderate/severe, which appears to be where you are at now. For me, at my next echo 6 months later, all three metrics had advanced and were in the severe category, and my diagnosis was then classified as severe aortic stenosis. For me it was a matter of months before I crossed the line from moderate/severe to severe. For you it could be years or that day might not ever come.
Aortic valve stenosis: evaluation and management of patients with discordant grading
Hopefully, you’ll find out a lot more about your condition in your appointment with your cardiologist. I would suggest writing down a list of questions that you have for him. Educate yourself, but no need to stress or rush. You have time, possibly a lot of time, before any decisions need to be made.