My daughter had an upper gi done when she was a day old the doc aid that she had gastric reflux, HELP?

I really dont know what to do to make her keep her food down she is gaining weight and her pediatrician doesn't seem as concerned about it as i am but sometimes she just seems to be in pain and arches back and let's out a forced cry she'll do that until she spits up about 1/2 oz of milk then she goes to bed she is on regular formula and also Zantac she was also taking metoclopram but that just seemed to make it worse so her doctor told me to stop giving it to her if anyone can please help me with some advice