breastfeeding and womanhood

So, I am going to start The South Beach Diet on Sunday, January 31st. I did the same diet in 2008 and lost 15 pounds while on it. Then, I found out I was pregnant. So, I couldn't continue because I was pregnant obviosly, then had my daughter, Francesca, and have been breastfeeding her. She is now almost nine months and she is starting to wean. So I figured it was safe to start this diet now. Currently I breastfeed Francesca twice a day, for 5-10 minutes each time. I think she will be completely weaned in about 4-6 weeks. I also have heard that a woman loses about five pounds after weaning a child so that will work out good. Francesca has been my best nurser so I am a little sad that she is weaning but I feel that it is time. I breastfeed my two sons for about 7 1/2 months each so ten months will be a great accomplishment for me.
I am a little worried about my hormones and emotional state because ever since my daughter started weaning I have been a little moody. I talked to a nurse at my OB-GYN's office and she said it was normal so I don't feel as bad and since I am expecting it I can prepare for it. Oh the joys of being a woman, I love it but, wow, dealing with the emotions is tough, for me and everyone around me I am sure. Also, my aunt said the first week of The South Beach Diet most people are grumpy. My husband, Justin said he will be completely supportive of me going on this diet so I know that will help tremenously.
In addition I wanted to point out that we don't plan on getting pregnant for about 4-5 years so now is a good time to lose the weight, because I can keep it off, at least for a few years.