It seems that more and more babies are being diagnosed with GERD, most of them are on medicine for it, and it doesn't really work. Babies spit up, it just happens. A muscle in their esophagus isn't fully developed yet. It is natural. Now the stomach pains (colic maybe?), that is hard to take. My son was diagnosed with GERD, but I didn't believe it because he had no problems with breast milk. When we gave him formula he was miserable. How could it be acid coming up his throat when it only happened with formula? We did extensive research and this is what we came up with:
***If she is formula fed do not give her the formula with the DHEA in it. I may have the wrong initials, but it is the oils to help with brain development. The problem with them is during the processing a chemical is used that binds with them and causes stomach pains in babies. If you are concerned with brain development, I would use a formula without DHEA and put good quality fish oil in my son's milk. Carlson brand consistently tests clear of heavy metals.
***She may have a problem with milk, either from you drinking it and it gets into her breast milk or her formula. After trying 5 different formulas the one that worked with us was Baby's Only Toddler Formula Lactose free. We also used goat's milk.
***There are a lot of other things in breast milk that babies react to. Onions are one, but do an internet search and find other things that may react poorly with baby. Try eliminating them from your diet one by one.
***For immediate relief, Mylicon worked for us. Hyland's colic tabs worked sometimes, you just have to give it a few minutes. Gripe water worked well.
***We put towels under half of his mattress so it slanted. Another trick is to place books under 2 legs of the crib to make a slant. Then put those foam stabilizers on either side under the arms so baby doesn't roll down.
*** The best advice we had when he wouldn't stop crying was this: sit in a rocking chair with baby facing out. Firmly rub your hands, one after another, from the bottom of her ribcage to the top of her pubic bone 15 times. Count out loud, it soothes the baby. Then bring her legs up to her tummy for a count of 15. Then rub her tummy clockwise (don't go the other way or the gas "backs up") for a count of 15. Bring her legs up again for 15. Repeat until she calms down. It usually didn't take more that three times and my son was happy.
***This doesn't sound like your problem, but I'll mention it just in case. My niece had colic really bad. My sister tried everything. When she took her for Craniaosacral therapy the crying stopped almost immediately. It only took two treatments and she never had a problem again.
Hope something here helps.
M.