3 months post op. nissen/laprascopic, robotic, hiatal hernia repair. recently experiencing painful, debilitating gas& diarrhea. is this normal?

Not from the surgery: It is very unlikely that these current symptoms are related to your surgery. By far the most common cause of diarrhea is viral infection (enteritis, or gastroenteritis if it involves nausea/vomiting). With any diarrhea, weight loss, dehydration (feeling like you're going to pass out when standing), or fever lasting > 1 day would be cause for concern. Otherwise these things tend to resolve.