It could be, or it might be something else. (Yeah, lousy answer, I know.)
It could be a reaction to a certain food, or a type of food, or a drink, or anything else you put in your body. It could be a food allergy or sensitivity. Have you ever had testing done?
It could also be IBS. The thing about IBS is that it seems like we can eat something one day, and be fine, and the next time we eat it, we suffer for it.
You're 55 - have you ever had a colonoscopy? That can help rule things out.
Are you under the care of a gastroenterologist? If you aren't, now would be a good time to get one.