Seeking advice

I told my fiance today that I wanted to stop breastfeeding as the newborn has not been gaining weight and it has taken a toll on me. I feel like I just can't do it anymore.. She recently spent 2 days in NICU for jaundice and ever since I feel like everything that goes wrong is my fault. Today he told me that I am stupid and that I'm being selfish for saying that. He told me he would be calling the baby's doctor to let her know of the "stupid" choice I wanted to make because I "just dont feel like doing it" anymore. My other 2 kids feel neglected because of how much time I give to the baby to breastfeed..I lose sleep over cluster feeding because he "can't" help me at night. He refuses to give her milk that has already been pumped while we transition to formula. He has been telling me all morning how stupid this decision is. He even went as far as to tell me that if she gets sick that it's my fault and that I've caused it. Then he sent me articles on how formula is bad for her. And how I should quit being selfish to put a 2 week old on formula. I feel so awful and defeated for wanting to make this change. I am so worn out and so sad of his reaction. I feel so unsupported and alone. I'm not sure what to even say or do. :(