Horrible feedings (gas/burping) - Alimentum vs Nutramigen

Our 5 week old is on Alimentum for a milk protein allergy. When we first switched to it, he did well for a few days but we’ve been on it for over a week now and he’s screaming through every bottle. It’s like he can’t seem to release any gas. We’ve been giving gas drops before every bottle. He’s also on Zantac for reflux but honestly I think it’s more of a burping/tooting issue. Sometimes I can get one solid burp about 2 oz in but he basically screams the entire last half of the bottle and is really difficult to settle after eating. We’ve tried tons of different bottles and have settled on Dr Browns.

I know Nutramigen is basically the same type of formula but I’m wondering if the differences in ingredients and the addition of the probiotic in it would make it a better choice? I had a fussy, reflux first baby so this isn’t exactly new to me but nothing I know to try is helping and I cannot continue listening to a screaming baby around the clock!