Had an echo that stated "essentially normal". said my three aortic leaflets are mildly thickened but open well. isnt that considered aortic sclerosis?

Yes: What the reader might have meant was that "there is no hemodynamic adverse effect" as a result of "mildly thickened" trileaflet aortic valve. But, yes, you are correct is making the connection to early atherosclerosis = sclerosis. Consider checking your fasting lipid levels and embarking on a heart healthy lifestyle if you have not already.