Nursing and (not) losing weight

Anyone else exclusively breastfed and not losing weight? With my first baby I was back to my regular size around 6 months, but he was on formula. With this baby I’m breastfeeding for the first time and I’ve plateaued- I have 10-15 lb left to lose and my weight has been the same for about a month now. Is my body trying to keep on extra weight? I’m slim to begin with, about 110-115.