Dairy allergy?

My almost 5 month old had a dairy allergy which led him to be fussy all the time only during feeding sessions when I started him on solids he would cry and eat. and he would also cry and eat while he would breast-feed. He weighs almost 14 lbs which is under weight for his age. And I figured out the underlying reason was because he had a dairy allergy which gave him acid reflux which led him to be fussy during feedings so he would never finish his feeding to where he was full. and that’s why he wasn’t gaining enough weight. So I had to start supplementing with hypo-allergenic formula and it’s very hard to find formula around this time as everyone knows there’s a shortage. I haven’t ran out yet but I cut dairy out of my diet and I’ve been supplementing with the formula so he has been gaining weight and he’s doing really good. But for two days he didn’t want to breast-feed at all and he would just scream and cry, he wanted the bottle. Maybe because he likes the taste of the formula better? I’m not sure. also it could be because my milk supply dropped sufficiently. I’ve been trying to pump and latch him but it’s a struggle to get him to breast-feed he doesn’t wanna put his mouth on it to begin with it’s not like he put his mouth on it and start sucking and nothings coming out he doesn’t want to even put his mouth on it at all he just wants the bottle any suggestions? I’d like to keep breast-feeding and I need to because of the shortage and I’m trying to get my supply back up I’ve been power pumping and trying to eat good and drink lots of water but it’s just taking forever for my supply to go back up.