What can it be?? Stomach

My husband had a stomach issue about 5 months ago.... constant diarrhea and then was fixed with some antibiotics, which tells me it was some kind of a bacteria or virus. About 2 weeks after all this, he started having a cramping feeling on his left side of his abdomen. It comes and goes throughout the day, but he’s had it for about 4 months. He went for a CT scan, and everything looked clear in his abdomen and kidneys. Anyone with similar experience? It’s so frustrating.