Periodically, without knowing why, I have severe abdominal pain. It comes in waves. At the same time, I am filled with gas and burp repeatedly. My Gastrointerlogist prescribed Nexium 40 mg before breakfast and Zantac as needed. I also use Tums. And, as a last resort, I use Levsin .125 mg as prescribed. These spells last 3-4 hours and create tough discomfort. I am experiencing a spell now. I will be most grateful for any info and advice.