Nutramigen working or not?

My little one has been placed on nutramigen. We started 3 days ago and yesterday was a good day but today he’s crying every time he has to poop or fart. Sometimes he doesn’t even end up pooping or farting. His little but is getting so red because he poops so often. But they are such tiny amounts. He calms down usually when I place him stomach down on my chest.

How long is it going to take to notice a change? He seems to be getting more gas out then before putting him on... which I assume is better then not getting it out. But he just still looks like he’s in pain. ☹️