What Causes Vomiting, Stomach Ache And Burping In A Child?

My daughter is six years old about a year ago she would wake up in the middle of the night vomiting, badly and it smells horrible, so does her burps, at one point her stools turned white. Took her to a gastro specialist, ruled out celiac, tested her stool for parasites etc. took blood work didn t find anything. Mysteriously she stopped but now almost a year later it s starting again. Her Lower stomach aches, she goes to sleep then wakes up busting with vomit, smells like rotten foul something I don t know what...I don t know what else to do...she also has this rash that the doctor says isn t contagious but only on her foot and by her knee it goes away and comes back... I don t want it to be something big and deadly and going undetected like now.