Feeling hopeless

I have a four month old daughter and my fiancé doesn’t really help bc I’m a SAHM so he thinks most of the responsibility falls on me. I’ve been dealing with PP and days like this where she isn’t in a good mood I feel like I can’t do this... I don’t know if I can be a mom or a good one at least. I don’t know what to do. Sometimes I feel like she would be better off without me.