Richardswife, I have to agree w/those who posted before me. I also have an AH who is exceedingly good at concealing his drinking. The only way I could ever tell was if he would "overshoot" and be obviously drunk. Other than that, I could never tell, and in the end, that's not what matters anyway. What DOES matter is if his behavior is something you want to live with.
In my case, there was never overt abuse or violence, but there WAS nonstop lying, emotional unavailability and just mostly the fact that he was not present in the relationship. He wouldn't remember things we talked about, he had no interest in doing anything that would take him outside the house (where he drank) or outside our usual routine (set up to allow him to drink).
And eventually I had to ask/answer the same question as you: Does it matter if he's drinking or not? What matters is this behavior--is this what I want from my husband? If not, the reason for it really doesn't matter. It's just plain unacceptable, and I need to make my own arrangements to move ahead, whatever they may be and in whatever time frame they maybe.
I'd like to suggest you try some Alanon meetings, if you haven't already. You might get some more insight and support there, too.