5-yr-old with GERD

Im looking for help with my 5-yr-old daughter with acid reflux (undiagnosed). For years now, she has complained of a 'pain in her heart'. She always burps a lot and frequently has a sore throat and 'sicky burps'. She likes to express her opinion and is a third and youngest child. She mostly eats small meals and needs encouragement to eat. 1 month ago she got a tummy bug (i think!) and was sick several times over a week. She carries a bag around since then incase she vomits and feels the need to in the form of acute sudden tummy pain (she points to her stomach) often. She feels better after vomiting. She has just started school and is very worried about her 'cross teacher'. Recently she has had outbursts outside school saying she is going to be sick and she can't go today. She was sick frequently over the school holidays and did not want to go anywhere. she can't be bothered to do much. its all too tiring for her. She loves to eat fruit and veg but does not really like rich foods. She is loosing weight and is slender. she is irritable and everything annoys her at the moment. She now cries a lot and says she can't stop. She loves to please and hates disapproval. Oh my husbands family have strong history of ulcer/GERD. Sorry long post. I'd hate to put her through scope and proton pump inhibitors. any ideas?. Seen Nat Phos 6x suggestions...but cant find dosage for age 5. Thanks so much for reading