Its always good to take a multivitamin, it just insures that your body is getting enough nutrients, i am going to assume that like during pregnancy, your body directs nutrients to baby, and to your
milk, so it is important to replenish those
nutrients so baby gets more as well. As far as milk production goes, i pump too. Pumping is not as effective as regular breastfeeding, but since i cant breastfeed i dont have very much milk and have to resort to formula sometimes.