Hugs, I think your ped is great
definately worth trialling. Did he put her on a reasonable dose for her weight? Often Zantac has to be the max dose to be effective, particularly at this age. Keep in mind to if it does make a difference that with every 500gm-1kg weight gain the dose will need to be adjusted.
If you can, elevate her cot too (I know at this age it's sometimes not appropriate, my boys were all over the cot
), try smaller feeds closer to BT, maybe a split feed, and minimal solids close to BT too. You can give pain meds too if things are really bad, but IME they just take the edge off, that is all. This is why you think - can't be pain, it makes no difference
Fx it helps, you should see improvement within a week xx