baby gastroesophageal reflux- natrum phosforicum

Good evening!
I need your help. I have a six month baby that was diagnose with reflux. He doesn't spit/vomits as much, as he did when he was smaller. He still arches his back, cries a lot (moans and sobs during the evening), when he burps cries also. we can hear the reflux and smell the acid in his breath, and sometimes see the milk residues. we have changed the breastfeeding position and rise the bed. It hasn't work. We went through several doctors until they discover this. So by now he has esophagitis (they think) and they gave us esomeprazole. It still doesn't do much. We have done just breastfeeding until last week, when we introduced soups. during the day it's hard but it gets worse during the evening. We end up sleeping sitting in an armchair.
He poops every two days. And has suffered also with colics, but now passes gas often.
I've heard about natrum phosporicum - i don't know if it's the best. I only have boiron pellets available in the drug store.

Please help!
Thank you for all the help.
best regards,