You did the right thing. Ten months and his alcoholism has progressed considerably...of course, it's also possible that he just hid it better in the early months.
You have less than a year invested in this relationship, you don't have children together, you haven't co-minged your finances or your living situation....walk away and know that you're doing the best thing for both of you.
It hurts but not nearly as much as another three or five or ten years spent trying to fix what is not yours to fix.