Need to rant : has anyone gone through this ?

Ugh I’m so stressed out 😞 my April 28th baby girl is a little off the growth curve , so she weighs like a pound less than she should ! But she sleeps through the night and everything, I just feel like the one thing that is literally my job and my responsibility (her eating) I can’t even get right 😕 I feel like I failed her and I feel horrible thinking that she hasn’t been eating enough , so now we started supplementing more , I just feel like maybe my breast milk isn’t heavy enough or fatty enough 😕