GASTRO/AUTOIMMUNE OR SOMETHING DIFF?

I am concerned about my 7 year old daughter. She has started complaining about having a "bubble" feeling in her throat. She says sometimes it is big and sometimes it is not. She does not want to eat because when she does she feels nauseas. When she gets nauseas she gets the chills really bad and begins to shake, have diarrhea. This has been going on since the beginning of March. She is not getting good sleep because this "bubble' wakes her up, she has dark circles around her eyes, and she is constantly tired. We have brought her to out pediatrician, they did an x-ray which she thought looked normal, bloodwork which was fine and autoimmune tests (celiac) which was negative. They put her on antacids and said it must be acid reflux, but the medication has not helped and the bubble in constantly there and my poor daughter is not herself and completely run down. I also worry because she has been sick since the end of December every two weeks with some sort of illness. The end of December she had 103 temperature and was having labored breathing, headache and cough at times - they said it was croup. She seemed to get bette than two weeks later had bad headaches, tired constantly, had stuffed up nose, hard to breathe they said they could test her for pneumonia but when listening to her chest she sounded ok. She got better for a couple weeks than end of January she had bad headaches, congested, body aches and tired all the time. They said it was a sinus infection. She got better for a week and a half and then came home one night after school and started vomiting she threw up at least 15 times and could not even lay down or take a spoonful of water or it would come right back up. She got better for a week and now we are dealing with this feeling of a bubble in her throat, headaches and nauseas all the time and this has been going on since March 7th. Oh and after they did her stomach x-ray that looked normal the radiologist called my pediatrician to say there is a tumor on her hip they found so we need to bring her back and do a hip x-ray. They said after the hip x-ray that it seems to be benign. I just worry with her immune system getting kicked down all the time and in a house of 6 she is the only one getting sick constantly. I don;t know if it is a gastro issue, auto immune issue, or what to do. My daughter asks me if she is ever going to feel normal and good again?? I am truly at a loss as to what might be going on with her, but just want her to feel better. Any ideas?