Husband not supportive of breastfeeding

My husband was really supportive of me breastfeeding during pregnancy and right after. He encouraged me to do it as long as possible. Well now he thinks formula is a cure all and will give us a miracle or something. His mom keeps suggesting it which is pissing me off. He thinks because she suggested if we give baby formula she will sleep through the night all of a sudden at 5 weeks old. That she will poop with put making a face and she wont ever fart again. 🙄🙄 we gave her formula at 1 week because she was losing too much weight and it made her so fussy and gassy but he insists it's my breastmilk. I'm exclusively pumping so this isnt a jealousy thing. I honestly just want to throw in the towel because at 5 weeks I'm so sick of defending breastfeeding. I just cant keep up emotionally anymore. He says I defend my breastmilk like I'm offended something could be wrong with me.....seriously I keep telling him no I'm defending what's best for baby this is not an ego thing about the quality of my breastmilk. Ugh I'm so frustrated