Hello, and I hope I can help you today. Encorate is a medication used to treat mood problems and/or seizures. The side effects of the medication can cause nausea, fatigue and headaches, so you may feel sick to your stomach which in turn has made you lose weight. It is also possible that the medication is not causing how you feel at all- and you have lost all the weight simply by breastfeeding your baby. You need a lot of extra nutrition while breastfeeding, so you should take a daily prenatal vitamin even as long as you are feeding your milk to the baby. One more important thing to know about Encorate is that it can be dangerous to take for a fetus while pregnant. So you and your husband should use contraception while you are taking this medication. I hope I was led to adequately answer your question today and that this information was helpful. Best wishes, Dr. Brown