B.F.
What you eat or drink has very little to do with your supply. Here's how it works: Your body will always give the best that you have to your baby. It will take all the vitamins, good stuff, etc away from you and put it in the breastmilk. So, if you don't eat healthy, your baby will still get the good stuff, but YOU may have your own resources depleted. (Ex. think of the mothers in third world countries that are sickly thin, but have healthy fat babies) If your resources get depleted, then you run the risk of getting sick/rundown which in the long run could affect your supply. I encourage you to eat well rounded diet with appropriate portion control. Portion control is important-many ppl get caught in the idea that they are "eating for two", and you aren't. You are eating for one! Please don't do any of the diets where something is avoided (no carbs, or no meat, etc). Your body needs all of the nutrients provided in food. It's ok to cut out junk food and fatty foods--things that provide empty calories. Exercise if you can, but don't over do it.
Be healthy, be smart. And give yourself time--your baby is still really little. Your body may react differently this time then it did before. It may not be like before when you didn't lose.
good luck mama!