Morning Peppy, firstly, good for you, a month IS an achievement, be proud of it and take strength from it. I have serious issues with alcohol and havent had a drink for almost a year now, and you know what, I dont miss it. Granted, my problems evolved over a 15 year period and escalated to mammoth proportions, but thats how its starts.
You should be proud that you have recognised something which is harmful to you (in all respects, not just physical) and dealt with it.
As for the weight gain, as styley and haysi both say, occupy your time with something else, exercise is brilliant for giving you that feel good factor, gets those endorphins flowing! There could be two reasons for the weight gain, alcohol can be an appetite suppressant for some so when you give up your appetite returns or you could be substituting food for alcohol, either way, a healthy diet and excerise will keep this in check.
Good luck and take care
warpig