Welcome to SR bighaircut. Alcohlism can sneak up on you over the years, i know it did for me. It's great that you recognize it and want to do something about it, coming here to SR is an excellent first step.
Regarding the worry of someone "finding out", most likely some already know to be frank - think about your friend who was over during your blackout for example. Your husband obviously knows too, and it's likely others do too. What's vital is putting those fears aside and taking action to solve the problem. There's lots of ways to go about it that don't involve publicly admitting the issue - private therapy, self paced sobriety methods like AVRT, anonymous forums like SR, self help books, etc.