Have to lose 40 lbs in 5 months to fit into my wedding dress

Getting married September 16th and my dress is strapless. I want to look beautiful and fit for my wedding and my honeymoon. Running everyday and partially doing brazilian butt lift (which literally kicks my butt). Eating 1200 calories a day which is hard since I have two kids and a fiance that eats horribly (and of course still looks great). I have gained about 15 lbs this year from eating his snack food that he leaves in the bedroom (he calls them table treats). Grrr.. I can do this though.

I am 5'6 and ranged from 125-135 until my second child then gained about 30 lbs. She is seven now though so I think I have to stop using her as an excuse. I'm 5'6 and weight 165 right now. My goal weight is 125 (size 4/6). Here is the dress. It sure would be nice to look as great in it as the model. LOL.

Here is the dress: http://www.maggiesottero.com/dress.aspx?style=S5094HP