My babe hasn't gained a single ounce in two weeks. The lactation nurse suggested adding a tsp of formula to my expressed milk. He has had a slow weight gain since birth. He was 7+2 at birth and now 11+4 at almost 5 months old. I am having a moral dilemma because I don't want to add the formula but I am concerned that he isn't gaining because my milk has a low calorie count. Any input??