Gaviscon yes or no?

Baby girl is 9 weeks and has reflux. She also has really bad infant dyschezia so is already struggling to poop on a good day. She strains and grunts for ages before she can pass poop. I’m reluctant to start giving her gaviscon (which is all the doctor keeps suggesting to me) as I really don’t want her to be constipated. What’s people’s experience with this? Does gaviscon help massively or is it not worth it if it’s likely to give her constipation? It’s like trying to pick the lesser of two evils!