First and foremost don't be too hard on yourself. Just take one day at a time. Do not make promises to yourself or others, simply "do your best" and that is all that yourself as well as anyone else could expect.
You obviously had a "slip up" last night. I will just say that being an alcoholic I have FINALLY come to terms with the fact that I CANNOT drink. I have tried to convince myself that, after being sober for 2-3 weeks that I could start back and that I could control it. Who was I kidding. I was right back into old habits before I knew it.
If you truly believe that you are an alcoholic, you simply cannot drink. I know it's hard and I'm not about to sit here and tell you that it's going to get easier because it's not. However, it is well worth the fight. I don't know if you are going to AA meetings or not but all I can say is that they have helped me more than you could imagine. The support from the members has been incredible.
Hang in there!