This sounds like my kids. My dd was a silent refluxer. Would arch and pop off mid suck- ouch. It took awhile to get her diagnosed and she was put on the prescription drugs. We tried a few different ones. Some worked better than others, but still not great. I had a fast letdown, which didn't help. I nursed on one side only per feeding. This helped some, but not entirely. She did learn to take in smaller amounts at a time to save her system, I guess. But what worked the best, taking her to a Naturopath. I know a great one for women and children in downtown Beaverton, if you are interested. She put my daughter on a probiotic (1/2 tsp of powdered Bifidous- but my dd was a bit older and glutemine -I think that was the other supplement). Within a week, huge difference, much better.
With my son, he was a spitter, same situation. The Naturopath put him on 1/4 powdered Bifidous at 2 weeks. Huge change within a week. I would start with 1/4 tsp of either a powdered Bifidous or powdered Primadophilous and finger feed it the dose, just let your baby suck it off of your finger or nipple until dose is gone. It is a probiotic and probably won't hurt your little one, but could help tremendously. When my ds was about 4-6 months the dose was upped to 1/2 tsp. and when he started solids, I could add it to that.
Also, prop up one end of the crib/bassinet so she isn't laying flat. My son also did 20 min. catnaps during the day and woke very easily - any change.
Let me know if you want more info, or the name/number of the Naturopath.
D.