Suggest Treatment For Bloating And Vomiting Despite Taking Simethicone

Thanks a lot. I have seen a military health doc for a situation that has arisen and persisted over past 11 days. I m a 67yo WF with unremarkable medical history. Had about 4 days of slight bloating, then vomited once and since then have had significant abdominal distention and bloating. Vital signs were and remain normal. No fever. Apparently supine percussion showed little tympany. However, abdomen blows up like a balloon when I stand up and walk. Somewhat relieved when I sit or lie down. Normal stools (not clay, dark or floating; no diarrhea; no subsequent vomiting or nausea); normal urine. MD Rx d Zantac and simethicone, but so far (48 hours) no relief to speak of. Any thoughts about what s going on and potential symptomatic (at least) therapy? Would love to hear your thoughts, as I m miserable. I m also an MD, but have been doing public health and research since completing residency in 1978. So my own second opinion on my own case is weak at best. Really appreciate your thoughts.