You need to have the GERD test done. If it's positive then the DOC should have prescribed medication.
Our doc gave our boy Liquid Reglan. It was a miracle drug. It relaxes the tummy so it will open and empty easier so the food going in won't come back up as much, the lower opening in the tummy gets relaxed too and it opens up more. SO the food goes through quicker and better. Then if he was having issues and not able to eat well the meds helped his food to go in and down really well.
Food will make this worse. Food makes the stomach produce even more acid. So if you're feeding her food of any sort that might be the root of your problem.
We were only able to start rice cereal and formula at 6 months and then it was another month or so before we could add anything else. We took food really really slow. Every time we tried to do food he'd get worse and have acid so bad he'd cry for hours. It also caused horrid gas in his tummy.
So, no food, only formula or breast milk and if you're nursing him you might need to cut certain foods out so they don't cause his acid pumps to go nuts.