I came back online this morning to look for info for you, but to be honest, I couldn't find an awful lot apart from the usual "seek medical advice" line....
so... I got my LLL book off the shelf (i'm a breastfeeding support peer by the way) and trawled through that - I have to say, I was surprised that there wasn't a chapter on breastfeeding and eating disorders, but i did find this bit of information for you:
"Crash diets, fad diets and quick weight loss present problems for nursing mothers. In the past, there was concern that losing weight too quickly would release environmental contaminants into the nursing mother's blood and increase the levels in her milk. However, more recent research shows that this is not a risk. Exceptionally high protein/low carbohydrate diets are potentially harmful for breastfeeding mothers because of the substances released into the milk by the mother's altered metabolism. Any kind of drastic weight loss carries the risk of a drop in milk supply. Good nutrition will also help you combat the fatigue and emotional ups and downs that are and inevitable part of new motherhood."
As Madmouse said, women throughout history have breastfed their children when there is little food for themselves, but you have to take care of your own health too. Even though your baby will be healthy, you have to be healthy for your child.
Try to focus on the positives when you have your baby, go with the flow, and like i said in my post last night, if it does start to creep back then you will be able seek advice then. I would also suggest seeking some sort of help now, while you are feeling well - maybe some advice from your gp about nutritional needs of your baby. I forgot to say yesterday, how strong you are in asking for info - you have clearly put your baby's health first - and you will need to put your health right up there too, to be able to care for him or her.
As I said before, all the luck in the world.