I need to fit into my bridesmaid dress in a month, help!!!?

I am going to be in a wedding in a month. I just tried it on and it's a little tight, I'm not trying to lose 20 pounds, that's unrealistic for me. I am a mother of a 1 year old girl and weigh 127 pounds. I don't have too much time to spend in the gym. I just came back from Hawaii and I ate more than enough food, I just want to fit into my bridesmaids dress. Help!!!