Premature baby help

My baby came premature (7 weeks early) & stayed in the NICU for almost a month. She got discharged the day before she made one month. I chose to want to breastfeed but they told me & her recent pediatrician also said that for every other feeding we have to add enfacare additive to my breast milk to give the milk extra calories so she gains weight where they want her to & my pediatrician has said that she’ll probably need to do this the whole year I’m breastfeeding. Lately I haven’t been pumping and I’ve strictly breastfeed her. Has anyone else done this? Or is the pediatrician going to tell me I need to start giving her the enfacare additive to my breast milk ?