Fat Burner for Breastfeeding Mommy

In a month time, I would need a fat burner! You can't diet when you are breastfeeding but I think it is ok to consume fat burner to burn excess fat on my body. I read that Phenphedrine is really a good fat burner but I need to do some research on the phenphedrine side effects. Every medicine has it's side effect. I need to know whether it will reduce my breastmilk production and whether the substance used is bad for a breastfeeding mommy and her baby.