5 month old with GERD

Hi,
My daughter is 5 months old and has reflux and a milk protein allergy.  After seeing a GI specialist 10 days ago, we switched her to Alimentum and she has been on prilosec for the same period of time.  Initially, she seemed to be better--- eating more and more importantly she seemed more comfortable.  Now, she is back to arching her back while eating, having difficulty burping and general fussiness around food.  The gassiness is interfering with her sleep as well.
We have added a few new things-
1. she started teething
2. we added sweet potato to her oatmeal.  We started on Saturday-- with the blessing of the specialist.  She initially loved it and gobbled it up. Yesterday she would not take any bottles for the rest of the day after the solids and today (thursday) she ate some and then cried.
3. she started rolling over so we stopped swaddling her at night.

We have tried Zantac, soy formula, rice formula-- none of these have worked. She sleeps on an incline, I hold her upright for 30 minutes after a feeding, we burp her after every ounce.

What is causing this flare up and what else can I do to make her feel better?