Irritable Bowel Syndrome (IBS): The patient's symptoms of abdominal pain, bloating, and changes in bowel habits, along with the absence of alarming features such as weight loss or bloody stools, make IBS a strong consideration. The periodic nature of the pain and its improvement with vomiting and lying down also align with IBS, although the elevated eosinophils might suggest an additional or alternative diagnosis.

Gastroesophageal Reflux Disease (GERD): Although the patient denies an acidic taste when vomiting, GERD could still be a consideration given the burping and abdominal pain, especially if the pain worsens after eating. However, the lack of typical GERD symptoms like heartburn reduces its likelihood.
Inflammatory Bowel Disease (IBD): The chronic nature of the abdominal pain, bloating, and the presence of elevated eosinophils could suggest IBD, such as Crohn's disease or ulcerative colitis. The fact that previous ultrasounds were negative does not rule out IBD, as these conditions often require endoscopic evaluation for diagnosis.
Eosinophilic Gastroenteritis: This condition is characterized by eosinophilic infiltration of the gastrointestinal tract, which could explain the elevated eosinophils and abdominal pain. The symptom of feeling like "someone's wringing out a washcloth" could be indicative of the intestinal spasms associated with this condition.

Appendicitis: Although the pain is described as being in the center of the stomach and lower abdomen and does not radiate beyond the midline, appendicitis can present atypically, especially in females. The worsening pain and the fact that it sometimes improves with positional changes do not rule out appendicitis, which is a surgical emergency.
Ovarian Torsion: This is another surgical emergency that could present with acute abdominal pain. The patient's denial of radiation of pain beyond the midline does not exclude this diagnosis, as ovarian torsion can cause severe, localized pain.
Intestinal Obstruction: The symptoms of abdominal pain, bloating, and vomiting could be indicative of an intestinal obstruction, which is a medical emergency. The absence of absolute constipation (patient reports regular bowel movements) does not rule out a partial obstruction.

Eosinophilic Esophagitis: This condition involves eosinophilic infiltration of the esophagus and can cause abdominal pain, difficulty swallowing, and food impaction. While it's more commonly associated with dysphagia, it could be considered in the differential for abdominal pain with elevated eosinophils.
Mastocytosis: A rare condition characterized by the accumulation of mast cells in one or more organs, which can lead to a variety of symptoms including abdominal pain, diarrhea, and flushing. Elevated eosinophils could be seen in some cases due to the release of mast cell mediators.
Abdominal Angioedema: This is a rare condition that can cause severe abdominal pain due to edema of the bowel wall. It might be associated with elevated eosinophils in the context of an allergic reaction or hereditary angioedema.