I was completely blindsided by my 22 year old son's alcoholism. It hit me worse than anything I've ever been through. I ended up at my Drs for an antidepressant and the counselor's for counseling. I beat myself up for months with "Why didn't I see it? Why didn't I know that was a sign of alcoholism?". I'd never known anyone other than my uncle who had an alcohol problem ,so it never entered my mind. AlAnon helped me learn not to blame myself. It's so common for people to say "Why didn't I see it sooner?". What you're feeling now is so normal. Try to find an AlAnon group near you and go to some meetings.