What should I do about severe reactions to H. pylori treatment with Pylera and metronidazole?

Subject: Opinion on H. pylori Treatment and Severe Adverse Reaction Dear Doctor, I am a 25-year-old female pharmacist seeking an expert opinion regarding my condition. Medical History: - I am a 25-year-old female pharmacist. - I underwent an upper gastrointestinal endoscopy. - Gastric biopsy confirmed Helicobacter pylori (H. pylori) infection. - Blood tests for celiac disease (gluten sensitivity) were negative. - Abdominal ultrasound suggested possible delayed gastric emptying (gastroparesis), but no definite diagnosis was made. My symptoms before treatment were: - Severe epigastric pain (just below the sternum). The pain sometimes occurred after eating and sometimes while I was hungry. Eating often relieved the pain temporarily. - Occasional acid reflux. - Intermittent diarrhea after meals. Treatment: My gastroenterologist prescribed: - Pylera capsules (each capsule contains Bismuth Subcitrate Potassium 140 mg, Metronidazole 125 mg, and Tetracycline Hydrochloride 125 mg). - Nexium (Esomeprazole). The prescribed dose of Pylera was 3 capsules four times daily (every 6 hours), as recommended. After taking Pylera for 2–3 days, I developed: - Extremely severe epigastric pain (10/10), radiating to my back. The pain became dramatically worse after starting Pylera and was much more severe than the pain I had experienced before treatment. - Severe headache (10/10). - Severe metallic/bitter taste. - Nausea. - Dizziness and imbalance. - Two episodes of diarrhea. - Mild fever. I have a history of developing headaches with metronidazole (Flagyl). For approximately the past five years, I have avoided taking metronidazole because it consistently causes headaches for me. I have even noticed that the smell of metronidazole can trigger a headache, although I understand this may not necessarily indicate a true allergic reaction. I went to the emergency department, where I received: - Intravenous Metronidazole (Flagyl). - Buscopan. - Metoclopramide (Plasil). My symptoms improved only temporarily, but the severe abdominal pain returned after the emergency treatment wore off. The following day, my gastroenterologist advised me to stop Pylera. He treated me with: - Intravenous Nexium. - Intravenous Ondansetron. - Paracetamol for the severe headache. After this treatment, my symptoms gradually improved over the next day. My gastroenterologist plans to restart H. pylori eradication therapy after I fully recover. My questions are: 1. Do you think my reaction was more consistent with severe metronidazole intolerance or a true allergy? 2. Would you recommend restarting Pylera, or would an alternative H. pylori eradication regimen be safer? 3. Do my symptoms suggest that further investigations (such as evaluation of the pancreas, gallbladder, or other causes of severe epigastric pain) are necessary? 4. Could metronidazole alone explain the severity of my symptoms, particularly the severe headache and the marked worsening of my epigastric pain, or should another diagnosis be considered? Thank you very much for your time and opinion.