J.,
For one thing, you and your husband need to sit down and agree that your son's mother needs to be aware. I would schedule a time for the three of you to meet and talk about this issue together as mature adults. Now is not the time for petty issues to be brought up and it is not the time for the blame game. Now is the time to set your disagreements aside and focus on your son and his needs. Obviously by his behavior he is letting you all know that the way things are going is not working for him.
He has a need that is not being filled and therefore, he is trying to fill it in destructive ways. It doesn't matter at this point whose fault it is, what matters is that the three of you get together and devise a plan to build a stronger relationship with your son so that his needs are being addressed.
Alcohol is very destructive to a family and should not be taken lightly.
At this point, you all could probably take one guess and you would know exactly why your son is turning to alcohol to fill his need. It could be that he has been the target of frustration or that his feelings have been ignored, or something different. Whatever the reason is, it's time to take action and pay attention to him and what he says. What does he complain about the most? What makes him feel sad or depressed? Is he heard when he speaks? Listen to him and instead of telling him what to do, just be there for him.
Make time to plan more time and activities with him and establish a new relationship.
Don't come down on him when he makes a mistake, simply give him appropriate consequences and let him know that you are there for him and that you love him.
He is at a crucial age right now and he needs the extra attention and understanding to get him through these "peer led" years.
Ask for his forgiveness in any area that you each have failed him and ask him if he can tell you (on a weekly basis) how you are each doing as a parent on a scale of 0-10. Ask him how you can improve as a parent and then listen to him closely without being defensive. Make an effort to work on the things that he brings up. Ask him what it would take for him to feel complete and content in life. Ask him if there is any way that you can contribute to helping him get through different obstacles that he may be facing. Ask him what makes him feel loved the most; spending time together, giving him praise(words of affirmation), giving him gifts, doing things for him (acts of service), or physical touch (hugs, back rubs, etc...) And then, be there for him. Have a daily or weekly talk about how things are going. Let him know that he is very important to you and that you will do whatever it takes to be there for him (even to put anger at his mother aside).
Shower him with love, the way he would like, and keep him close. At this age, you can either give him up to the world or you can fight for him. He needs to know that he is worth fighting for.
Take Care,
T. (mother of 4)
P.s. As for the drinking, my 20 year old decided to try smoking cigars one time. I found the wrapper in his room. I printed up the "Dangers of smoking cigars (and anything else)" on the computer and highlighted the one's that I knew would affect him personally for his future, like "erectile disfunction", with a bright yellow highlighter. I then taped it on his wall in his room. Later that day, he came to me with a sheepish grin and said, "OK, I am definately not going to do that again!" He quit and still laughs about that letter today. He says, "Boy, mom didn't have to even say one single word to me, she knew exactly where to 'hit' home!" I haven't had any other issues with him since. Maybe he's afraid of another letter???