Both my boys struggled with this as babies, the first to an alarming degree; screaming and vomiting after feeding, crying for hours as I held him, walking and singing until his tummy would feel better, only to have it happen again next time he ate. It turns out that the underlying problem that contributed to the acid reflux was an allergy to milk and soy proteins that in most babies is outgrown by the age of 9 months. I am not a doctor so the way I explain it might seem simplistic, but basically the intestines of the baby are not always fully developed at birth and there are microscopic fissures in them that allow proteins to irritate the lining, causing stomach distress, diarrhea which is frothy/has mucus, and other gastrointestinal trouble.
Here's how we found it: I nursed him but he would scream and projectile vomit after each feeding when he wasn’t having viciously acidic diarrhea attacks. We saw the pediatrician almost daily the first 2-3 weeks. We tried soy formula (before we knew it was a proteins allergy) which made it 10 times worse, we tried Alimentum and Nutramigen which also didn’t resolve it (although Alimentum was probably the one that helped the most). So after about 4 weeks we went to a pediatric gastrointestinal doctor when the other formulas and acid reflux medicine didn’t work. The Ped GI said “treat the problem, not the symptom.” I cut all dairy and soy from my diet and tried to keep nursing but it was only half better. So on her advice, we put my son onto a formula called Neocate, and literally within hours we saw improvement, and in less than 2 days he stopped vomiting/diarrhea/acid reflux and started gaining weight. We continued the antacid for 1-2 weeks but by then the problem was gone. He was on Neocate (and I still nursed him restricting all dairy/soy from my diet) until about 7 months when we went to part Neocate/part Alimentum, and then by 9 months all Alimentum. We delayed milk and soy from his diet until he was 1 year old, and he’s been great since. When my second son had the same initial problem, we went right to Neocate and he too was fine.
Neocate is only available by special order through a pharmacy (usually takes 1 day to get it in) or from a children’s hospital, and it is terribly expensive, but it works. It was explained to me that it is as pre-processed a product as you can get, basically broken down to the simplest nutrients (amino acids) possible, and thus less likely to irritate the GI tract. It was $35 a can, and a can doesn’t even last a week, but I would advise you to try 1 can to see how she does. It can take a couple of days for her system to settle, but once it does, if it works, you will almost cry with joy that she finally has relief and you can have this thing called “sleep” once again in your life. If Neocate works, you can save money on it in a couple of ways: ask your doctor to write a prescription for it, and turn it in to your insurance company (ours didn’t pay but some do). Since our insurance didn’t cover it, we saved the receipts and itemized the cost on our taxes, which gave us some money back. I also started ordering it online by the case directly from the manufacturer (1 case was 4 cans) and that saved about 20% and had free shipping. It was a lot of money to us, but in the end, it was worth it to make the pain go away and to help him put on weight and grow. I used to tell my husband that our son was drinking his college fund, but today when I look at my health, happy 5 year old, I don’t remember the cost so much as the absolute relief I felt when he didn’t hurt anymore.
So for us, turned out that acid reflux was just one symptom of several, but when we finally figured out the underlying problem, all symptoms went away. We never gave up, and our pediatrician and pediatric GI never gave up, and I hope you can find ones as good as ours - we were very lucky to have them. Best of luck to you, my heart goes out to you and your daughter.