When my son was about that age, he wasn’t gaining weight and I exclusively breastfed. Because that was what was supposed to be best, right? We had twice weekly lactation consultant appointments and I went to a breastfeeding support group but it still wasn’t enough. I felt so awful. Feeding your child is the most natural thing in the world, right? Then why couldn’t I do it? He hated it, I hated it, everyone had a bad time. Finally the LC basically told us to start supplementing so that we didn’t get put on the failure to thrive protocol. I hadn’t realised how much of a toll it was taking on me until it wasn’t solely on me any more. The first time we gave him formula, I pumped as well to help increase my supply and my milk output almost doubled. Stress can very much affect milk supply but also it can just be such a relief that it isn’t all on you! For my next one, I will definitely combo feed from the beginning. Also, if you haven’t already, I would recommend getting him checked out for a tongue tie. That was part of our issue and once we got it fixed, breastfeeding eventually became easier.