The links below will provide you with more detailed information on these medical conditions from the WebMD Symptom Checker and help provide a better understanding of causes and treatment of these related conditions. Symptoms of heartburn and GERD are a burning feeling in the chest, throat, or mouth, nausea, and more. Medication side effects include nausea, vomiting, stomach upset, weakness, dizziness, seizures, and more. Antibiotics can cause stomach pain, diarrhea, nausea, vomiting, itching, rashes and dizziness.