They don't need to understand. And if they don't, despite what you tell them then they're either not your friends, or they have their own problems with alcohol.
Also, if you're trying to get sober yet hanging out with a drinking crows, well... ya might want to rethink that. It's not the most supportive environment for a life of sobriety. If you haven't already started going to meetings you might want to give AA a go.