reflux mspi

Emily • Mama to Leilani and two chihuahuas ♥️
Okay long story short, I was breastfeeding, bubs had blood in poop very fussy and unhappy. Got admitted to hospital (they thought intersusseption 🙄) diagnosed with mspi. Eliminated dairy and soy and other allergens from diet, no change. Bubs started losing weight, bubs put on elecare formula. Started to improve, started gaining weight, seems happier... now she has reflux  😑 elecare is very thin and comes up easy? Pharmasist suggested a thickener but I want to avoid any constipation as I feel this would be just as uncomfortable for her as the bloody reflux. Also the thicken says may contain TRACES of milk... I know that means it made in the same factory as milk products but that's a pretty big risk for my bubs. 
Anyway I'm generally just looking for ANY sort of advice as to how I can tackle this. Should I try a different formula? How much thickener should I use to avoid constipation but see improvement in baby reflux? Should I see if dr will prescribe something for reflux? What could they prescribe? Why is feeding a baby so bloody hard!!? How are you tackling mspi and reflux with your babies? Just looking for answers and some support.