indirectvictim

I know there are probably a lot of posts on this forum telling about the same problems, but I just feel an urge to share my experience. I don't want to talk about it to my friends/family, it's easier here where there are people who can relate to it.
I have been dating this great guy for a month when I first noticed his drinking issues. He would come to my place, and would constantly go to his car for various reasons ("I left my cigarettes", "I can't find my phone", "I think I left my wallet in my car" etc). I never had an experience with alcoholics before, so I believed all these stories until I started to smell it on him, and to notice that he becomes clumsier after every trip to his car. I confronted him, he admitted. He told me about his 2 DUIs, meetings with a counselor. I should have run away, but I did not. I continued dating him, it has been over four months now.
He is the sweetest guy when he is sober. Unfortunately he is not sober too often. Every time I confronted him, he either started a fight, or promised to stop drinking. He drinks every time he comes to see me, so eventually I got fed up, and told him we should take a break until he solves his issues.
I was naive and stupid to expect him to fight for me, to promise to stop etc.
He did not do any of these, he just left. He texted me it will take him some time to get over me, but he'll be fine.
I am broken hearted. We had plans to move together, he was constantly talking about marriage, about how much he is in love, how special our relationship is. Yet, he chose alcohol over me.
I just can't understand how this could have happened...