Will I gain weight during my menstrual cycle doing the atkins diet?

I am currently on the atkins diet. I have been on the diet for 7 days now and have lost 6 lbs. I will be going through pms this upcoming week and will start my cycle on Saturday. I was just wondering will I gain weight when I am on my menstrual cycle while doing the atkins diet? If so, how long will it take to come back off?