I was a periodic binger, but I wasn't really able to moderate in between. I'd drink 2-3 days out of the week, and then maybe go another week without drinking. Truth be told, I usually *needed* that time to get over my acute withdrawals in order to be 'ready' to drink again.
Water - congrats on taking action in recovery. Like Scott said, you may never know the reasons behind your particular pattern. Or maybe further into recovery you may gain some insight into it.
But as others have said, don't get too hung up on it at this point. What matters right now is learning how to prevent that first drink.