Can i take a hair vitamin while i'm still on prenatal vitamins and also breast-feeding.

Should be okay: .. as long as it is a naturally occurring vitamin that would normally exist in the body. If it is artificial, even without knowledge of the exact substance, I would recommend against putting in your body while you are breast-feeding your child. Just know that whatever you are trying to do to help yourself with these vitamins may very well end up working on the infant as well.